Monster a GoGo is a 1965 science fiction horror film directed by Bill Rebane and Herschell Gordon Lewis who remained uncredited in association with this film.
The plot concerns an American astronaut, Frank Douglas, who mysteriously disappears from his spacecraft as it parachutes to Earth. The policeman in one scene inspect the landing sight of Douglass capsule and notices a burned patch, only to dismiss is as a prank. The vanished astronaut is apparently replaced by or turned into a large, radioactive humanoid monster. This is revealed when it comes into the scene and kills off Dr Logan. A team of scientists and military men also attempt to capture the monster and at one point succeeds and imprisoned in the lab, only to have him escape. Neither the capture nor the escape are ever shown, and are simply mentioned by the narrator.At the end of the film, the scientists later corner the monster in a sewer under Chicago, but the monster suddenly disappears. The scientists receive a telegram stating that Douglas is in fact alive and well, having been rescued in the North Atlantic, perhaps implying the monster was an alien impersonating Douglas. The narrator provides the films closing dialogue ........
Source: Wikipedia