The problem is that zombies are pretty strongly typecast into survival horror, so you have to do something which breaks the mold.

Something should happen which doesn't fit the typical zombie game... something unusual and mysterious, which prompts investigation.

The most basic idea is a cure. For example, make one character turn out to be immune, and have them backtrack to find out how this happened and if there's a cure. Use the cure as a kind of MacGuffin to lure them into finding out the source, and discard it as a plot device once they know the source of the outbreak.

Another possibility is the outbreak doesn't spread from person to person; it obviously comes from a specific source... rip a page out of Aliens: victims are either eaten completely (ie not rising) or they are carried off to some kind of nest where they are exposed to the contagion. Make it really obvious that the zombies are "choosing" people; have them sniffing and groping people before hey get carried away.

But the point is you have to break the zombie-survivor-horror mold; establish clearly that the zombies are a stylistic element in a different kind of game.

I agree that you need to show the players (i) that they will all die if they don't investigate, and (ii) if they do investigate, they may live.

Aqui estão algumas idéias.

(i) Give a rather insane person a MacGuffin that makes the zombies avoid them like, well, a plague. This shows that there is something useful to discover. Since this person can wander around at will, they can visit the PCs whenever they feel like it. Of course, this person won't willingly give the item to the PCs, nor can/will they explain what it is or how it works. But if the PCs can works out who the person is, then maybe they can get on the trail. Make it so the item only protects one person, so that even if they steal it, it's not a complete solution.

e / ou

(ii) Have a mad scientist show up who claims he can solve the whole problem, he just needs some help. Cue dangerous but not suicidal missions. Certainly he has a nifty device that deals with zombies quite effectively, although it has several problematic drawbacks. Of course his ideas are only about 50% correct, and his over-reliance on theory will almost certainly lead to his rapid demise, but if the PCs can figure out which bits are right and which are wrong, and finish the job properly, they have a chance. If it's a problem to get him to the PCs, he could exist only on the end of a phone line.

e / ou

(iii) Use the TV to give clues. "Scientists are appealing for anyone who knows about [insert PC specialty here] to come forward" There's no way to get to these scientists, but they clearly have something in mind. What could it be? "Police urgently want to speak to a man called Terry Holden who they believe may have valuable information about how the outbreak began" One of the PCs knows who this guy is, or was. Etc.

Additionally and optionally...

(iv) Take a leaf from Daniel Solis's Dead Weight, and give the PCs a transport system that the zombies can't use. Make it clear that this isn't going to last for ever - as the zombies get more numerous, they will eventually be everywhere - but for now, it allows the PCs to get to islands of relative calm, until the zombie mob catches up with them. Daniel used parkour but a subway system could be an alternative. Most of the stations have been locked up, and zombies who get on the lines die of electrocution. If the players can get into the tunnels and either commandeer a train or just avoid stepping on the rails, they could go places. How you show the players this depends on the setting, but there could be a whole resistance movement down there. After a while, of course, the brownouts begin...

Is this kind of thing you had in mind? My first answer here, so feedback appreciated.

If you're doing the "reveal" of the zombies in a typical survival-horror way—zombies jump out and start trying to eat the PCs—then the players are going to follow that trope. If you can break the expectations of the survival-horror genre then you'll have a chance to supply story developments to communicate that this is an investigation game. This is necessary even though you're using a relentlessly investigation-focused system like GUMSHOE because a Jogo de interpretação de papéis trope of survival-horror is to introduce the genre with a bait-and-switch.

There are two ways I can think to defeat this.

Unrecognised threat

When you introduce the zombies, make sure the PCs are not immediately, personally threatened. Give them time to be observers of the phenomenon. Ideally, have them Apenas acontece to be located somewhere safe—for now—where there are overwhelmingly-obvious resources for them to begin their research. Their next step should be obvious to all, and it should be "research those zombies" rather than "run for your life." A private library devoted to collecting the written works of Vodouns, for example, or the Institute for the Integrated Study of Vital Essence and Biological Science.

Of course, the PCs will still want to barricade themselves, if only to avoid interruption of their research. Softly resist this, by refusing to provide a justification for their defenses. The countryside outside the institute remains green and pastoral, the flocks of sheep grazing the hillside and the shepherds moving about apparently unconcerned. Telegraphs arrive asking why the PCs have missed appointments, in apparent confusion.

However, you still want the investigators to take the threat seriously. You can do this by making the zombies threatening, but a threat that's unrecognised by anyone other than the PCs. Sprinkle the pastoral reassurances with indications that the zombies are not contained, and that nobody outside really recognises their nature nor the threat they pose. A passing newspaper reports a man biting another in a dispute in a nearby county, causing the second's hospitalisation. Zombies are mis-identified as rabies victims and restrained in hospitals. Others are identified as victims of dementia and put into asylums. A politician's departure to the Continent on an ocean liner is covered, and there is a passing reference to yesterday's story about that same politician being accosted by a madman who bit him, but the politician is soldiering on to attend the Leaders Convention in Munich. Make it clear that the public response to the zombies is actively making it worse by moving the zombies around and by not taking the necessary steps to secure them. Spur the investigators to action by showing them how their self-centred inaction is making things worse for them, not safer.

Contained but nasty threat

The zombies are an immediate and extreme threat to the PCs when discovered, but they're not able to immediately bust out and begin the zombapocalypse. They're at the bottom of a mine shaft that broke into an ancient tomb, for example. The PCs go to investigate, meet zombies, do the horror-survival thing… but in the light of day outside the mine shaft after their escape, it's clear that the zombies aren't an immediate threat. They're nasty, but of more concern is where they came from in the first place. Perhaps there is a timer on their research, in that the mine is about to be re-opened and the local authority will not hear opinions to the contrary. The researchers need to uncover the source of the zombies and deal with it before the new mine shaft is completed and connects with the old mine tunnels or the tomb itself.

The answer starts from the thinking man's response to zombies presented by John Ringo aqui.

Zombies, fundamentally are dumb. (or if they're not, we lose.) Attracted by noise, etc.

The first trick is to ensure that the characters don't conhecer it's a zombie game. Instead, they're, for example, police, investigating an IED in a cemetery with a remarkable amount of carnage. A group has read Ringo's note and functionally deployed it against a small outbreak of zombies (though the fact that they were already dead at the time of the explosion wouldn't be apparent yet.)

This demonstrates that zombies can be easily dispatched if the players don't fall into the survival horror mindset e that NPCs are already doing it. The first couple investigations will be these "domestic terrorist" incidents, which gradually reveal "oh no, zombies!"

Of course, these "domestic terrorists" (read: survivors) are keeping the outbreak pretty well contained, and stigmergic communication suggests these techniques to groups around the country... who have to deal with zombie outbreaks in their cities. The players, being the first cops on the scene are drafted/pronounced experts/from a special group/PlotReason into investigating the various outbreaks, which expands into "Who did this?"

The moment you threaten the players with zombies and no resources... they'll go back to the horror mindset. Keeping the players as government coming in during/after the fact and trying to figure out what's going on as well as spinning it for the media: that's where you'll get the gumshoe and zombies game.

Here's a rough 5 act structure. The following scenario is designed to give stealable ideas for your game, in the sense of fleshing out the ideas above. It shows how the zombies are kept at one remove, and players are given time to observe, orient, decide, and act. They should conhecer zombies are out there and have real resources to draw on before any zombie threat shows up.

This is one example of how that could work, the structure itself is roughly a 5 room dungeon:

Domestic Terror, IEDs, and Graveyards.

An Investigation in 5 parts.

Act I: Improvised Explosive Devices ... in the graveyard?

Characters are paged with a "get here now, there was what sounded like a huge firefight and the entire graveyard's on fire."

Vital Clues:

• Complex device at the center of graveyard, characterized as IED, solidly built, attack must have been planned for years
• Possible gang warfare as there are too many burned and charred bodies acima chão.
• Graves have been disturbed

Spends:

• Some bodies have flesh trapped in their teeth
• Way too many mais velho bodies above ground
• Older bodies look like they've been moved in rings around the device
• Device has a "lightshow" function which displays bright moving lights, sounds, and what sound like screams.

Act II: The meat-grinder

Garbage collectors call in emergency call when they find dumpsters full of ... blood? And chemicals sprayed all around. Biohazard!

Vital Clues

• DVD with a "how to protect yourself from the coming zombie apocalypse" on the cover, experts suspect that it's a terrorist coverup.
• More sophisticated IEDs, including a lure above a huge meatgrinder.
• Inside the structure, a "normal" person shot through the head, only other visible injury is a large bite on forearm. Body has had eyes closed and moved after death.
• Following trail of bodies back to another cemetery, signs of a ritual being performed

Spends:

• Person who made the ritual watching Bruce Campbell movies on DVD player before hand
• [lots of fun details about both sides]

Act III: Wait, zombies?

Autopsy of corpse. Corpse gets up during the middle of the autopsy. players shoot it down (or room goes up in flames. Remember, threatening players with danger = they go into survival horror mode. They've got resources on their side. They've got the military on their side.)

Vital Clues:

• Corpse has strange [vector of infection] in blood stream.
• Belonged to registered survivalist group in [location]
• Survivalist group has published "How to survive the zombie apocalypse"
• Records for the group

Spends:

• [more support for vector of infection.]
• [more details of the survivalist group.]

Intermezzo: The Clubhouse Agents show up at group's clubhouse, asked some non-sensical questions, allowed inside. Group explains what they know about [vector of infection] and proof of the uprisings.

Act IV: Showdown

With evidence for the [vector of infection] the agents head to [badGuyLocation] to arrest the person behind this. Have to shoot through house full of zombies. Action-horror rather than survival horror. Let them have plenty of blam and prep. Allow them to indulge in creative IEDs demonstrated in first 2 acts.

Vital Clues:

• A pamphlet: "So you want to raise the dead..."

Act V: Zombie Publishing Warehouse

Warehouse, small company, everything normal. When agents arrive there's a scream from inside, and a mail-truck turning around the corner. Small lab inside, the inventor has infected themselves with [vector of infection]. Small shootout, should be no trouble if the group closes the door to the room first, then secures the room. The zombie threat has been neutralized ... right?

Vital Clues:

• Mailing list for people who ordered "so you want to raise the dead."

Pensamentos

The essence of this is that the characters are functioning as investigators first and survivors second. They are approaching the problem with resources investigators can bring to bear: they have overwhelming force if they want it, they have resources, soldiers, and support. They estão the cavalry. They are at one remove from the zombies, and can view the problem in a detached light. By giving them time, distance, and resources, you don't break their OODA loops and trigger "Oh crap! Survive!" responses. For most of the scenario above, they are reacting to reactions to zombies, rather than zombies themselves. By presenting evidence of zombies, without the zombies, the players can indeed arm and prepare against a described threat, neatly neutering any horror or panic that the players feel.

Other recommendations

My other recommendation starts with a quote from the Esoterrorists's book:

In a horror game, mayhem suffered by the protagonists is not an impediment to forward movement. Horror characters are expected to die early and often. The player creates a new designing scenarios character, the Ordo Veritatis ships him to the scene, and bingo, you’ve got more meat for the grinder and the story continues.

Make it very clear that the players belong to an organization and that their observations will survive. If some fall to zombies, reinforcements show up next scene and play continues. That way, characters themselves are not scarce resources.

Extend the threat. Part of the reason that zombie-outbreak results in immediate hiding and barricading on the nearest, self-sufficient island probably lies in the sheer ruthlessness of the mechanics of expansion and infection. Make it very clear from the get-go that the infection rate from this infection is não going to immediately take over the continent: there are all sorts of ways to do that, and most of them should get left as an exercise to the reader, however, here's one.

This particular infection faz result in zombies, but the walking dead only arise after they die from other, more mundane means. That is, a zombie bites, you are infected. But it's like a bug bite: it's not gonna kill you. But when you die, you will rise, and you will crave human flesh. This gives a reasonably long infection rate and can riff on all sorts of horror: it follows an AIDS-like horror curve rather than an Ebola-like horror curve (as the traditional zombie pathology seems to).

This makes it easier to contain the threat, and gives people time to determine how the disease works and how to counter-act it. It might also completely change how people treat death: cremation might become much more popular, even legally required.

Twist the zombie threat.

1. Make your player characters immune to the cause of the "zombie disease", and do make them aware of this. Show that even if they wanted to, they can't become zombies, and zombies are utterly uninterested in them. An example of how to explain this: They have just arrived in a metropolis - and the zombie plague affects / can spread to only those who've been drinking / using (for washing etc) the city's tap water for at least a year.

2. As 1 alone might leave the players unmotivated ("So? Let's get out of here then."), introduce personal crises: Though they themselves are immune to the zombie plague, some of their beloved and other crucially important people (scientists, spies etc possessing critical campaign info unrelated to the zombies etc) living in the city are not... in fact, they're already in the process of turning into walking dead. The PCs must find the cure. (And if you wanted a bit of the survival horror back, get them to protect the important people. If you want pure investigation, without time pressure, those people are already zombies: given the cure, they can be turned back, but they're not getting worse, the PCs have all the time in the world to investigate.)

Jagged's suggestion, that players have personal objectives that means thay are strongly disposed to investigate, is good, but requires some handling. Now if you were playing in Glorantha, it just so happens that Humakti death cultists have a religious obligation to exterminate undead...

Something simpler is to let the players barricade themselves, where it just so happens that the most obviously defensible location that the players inevitably choose happens to be where there is a treasure trove of information that starts of the investigation and gives a strong and reinforceable hint that getting out and solving the problem that is suggested in the information trove is the path of maximum survival probability.

Perhaps if they had a name that wasn't Zombie. I know this sounds trivial but if you called them Voids or something it might cause a different attitude to them. Perhaps if the first sight of them was some NPC doing something less threatening to them, like harnessing them to a cart?

I would tackle this by ensuring each character has one or more personal objectives that ensure they won't want to just hide away. If you feel creative you can turn these into mini-games and offer rewards for their completion. This can work well for one-shot games but for longer campaigns you'd need to ensure they were worked well into a character's background.

For example if one of the main objectives of the scenario is to find out what happened to X you could give one character the objective of finding something X was supposed to be carrying.