The Andromeda Strain (1971)

When virtually all of the residents of Piedmont, New Mexico are found to have died after the return to Earth of a space satellite, the head of the US Air Force's Project Scoop declares an emergency. Many years prior to this incident, a group of eminent scientists led by Dr. Jeremy Stone advocated for the construction of a secure laboratory facility that would serve as a base in the event an alien biological life form was returned to Earth from a space mission. Stone and his team - Drs. Dutton, Leavitt and Hall - go to the facility, known as Wildfire and try to first isolate the life form and to determine why two people from Piedmont, an old wino and a months old baby, survived. The scientists methodically study the alien life form unaware that it has already mutated and presents a far greater danger in the lab, which is equipped with a nuclear self-destruct device should it manage to escape.