MacGyver and Pete are testing a new security system at the Strategic Research Development Administration. MacGyver successfully bypasses the security and meets Dr. Jill Ludlam, the system's designer. She tries to turn off the security system, but it doesn't realize that it was just a test. MacGyver and Dr. Ludlam are then forced to find a way out, as the security system, named Sandy, tries to destroy the "intruders".

Gordon Shumway, last known survivor from the planet Melmac, crash-lands his spaceship into the Tanner family's suburban garage. Willie dubs him "ALF", short for Alien Life Form. After convincing a military officer that they are not harboring a space creature, the Tanners decide to take ALF in as a member of the family.