S2·E25 Call of the Unknown

Able Squad blasts its way into the alien complex, and is pursued inside by Typhonus and his troops. After a battle which is made more difficult by interior defenses, Able Squad escapes into a different section. Meanwhile the alien structure begins to grow out of the ground. After the exosquad has blasted its way out and come to the aid of the jumptroops with Professor Algernon, the spire begins emitting great energy waves.