Xtro 2: The Second Encounter

The name of this movie is Xtro 2: The Second Encounter released in 1990-05-04 and it's main theme is Scientists at a secret underground complex have found a way to travel to another dimension. Three dimension-travellers are the first to go through the gate - but are soon attacked by something that interrupts the communication with Earth. This horrible something uses the gate to travel back to the underground complex. Most of the staff are evacuated, except four heavily-armed militaries and Dr. Casserly and Dr. Summerfield who just can't stand each other..