The Blob (1958)

Out on a date one evening, teenagers Steve Andrews and Jane Martin are parked in a secluded location looking at the stars when they see something fall out of the sky to the ground off in the distance. They go looking for what the falling object is, but instead find an elderly man they don't know in medical distress with something on his hand, he who they drive to Dr. Hallen's office. They are able to catch Dr. Hallen just before he was about to leave to attend an out of town conference. What no one yet knows is that the gelatinous mass covering the elderly man's hand was inside that falling object, it an alien life form that is looking for flesh to consume to be able to grow. Steve is the first survivor to witness that gelatinous blob totally consume someone to death. While Jane believes Steve's story, he is unable to convince anyone in authority, including the police, of what he saw, namely that there is a deadly "monster" for lack of a better word that threatens the survival of everyone in town. Steve and Jane go on a mission to find proof of the existence of the blob before it's too late, and even if they do find it, they, with anyone else they are able to convince of its deadly nature, have to find out a way to kill or neutralize it.