Another sequel with nothing in common with it's predecessors, this time taking place an a remote island, where a group of US marines, lead by Major Kirns (Sal Landi), are sent to a former gunnery range off the California coastline, to look for and remove any unexploded bombs that still may be lying around.
The group are told very little about why the navy want them to clear the island, other than they are looking at possibly building a refuelling depot there. But they are somewhat puzzled as to why this requires the presence of a Naval intelligence officer named Fettermen (Andrew Divoff).
When they stumble across a pit filled with human remains they realise something is definitely not right, particularly when Fettermen suddenly disappears with the boat leaving them marooned. As they search the rest of the island they discover what appears to be the remains of an alien spacecraft entombed in concrete and what appears a former military camp. But before they can figure out a way off the island they find themselves being picked off by a strange alien creature that has emerged from the crashed ship.
Also starring character actor Robert Culp and directed again by Harry Bromley Davenport, the film blatantly rips off scenes from "Predator", that alien autopsy video that was shown on TV during the 90's, and even "ET : The Extra Terrestrial" believe it or not. Be that as it may though this is still arguably the best of the three Xtro films that have been made to date. Not award winning sci-fi by any stretch of the imagination, but is still good fun on a trash level.