Provavelmente O Quatermass Xperiment de 1955, sendo o título de lançamento americano The Creeping Desconhecido .
Three astronauts are launched into space aboard a rocket designed by Professor Quatermass, but the spacecraft returns to earth with only one occupant, Victor Carroon (Richard Wordsworth). Something has infected him during the spaceflight, and he begins mutating into an alien organism which, if it spores, will engulf the Earth and destroy humanity. When the Carroon-creature escapes from custody, Quatermass and Scotland Yard's Inspector Lomax (Jack Warner), have just hours to track it down and prevent a catastrophe.
....
Quatermass and Briscoe determine from the evidence at hand that something living in outer space has entered the ship, dissolved Reichenheim and Green in their sealed spacesuits, and evidently entered Carroon's body, which is now in the process of being changed by this unknown entity. Not knowing any of this, Carroon's wife, Judith, hires a private investigator, Christie, to break her husband out of the secured hospital. The escape is successful, but not before Carroon smashes a potted cactus in his hospital room, fuses it into his flesh, then kills the private investigator and absorbs all the forces of life in his body, leaving just a shrivelled husk. It does not take long for Judith to discover what is happening to her husband; Carroon flees and disappears into the London night, leaving her screaming outside the hospital, alive, unharmed, but entirely mad from fright.
Inspector Lomax then initiates a manhunt for the missing Carroon. After hiding out on a river barge, Carroon encounters a little girl, leaving her also unharmed through sheer force of willpower. Then, Carroon proceeds to a nearby pharmacy and kills the chemist, using his now-swollen, crusty, cactus-thorn-riddled hand and arm as a cudgel and leaving a twisted empty husk of the man to be found by police....