Doctor Hans B. Trottlestein (scientist extraordinaire!) has been conducting some entirely ethical and perfectly controlled tests* in order to observe the prowess of his dazzling biological creations before he releases them into the wild. And you just so happen to be the latest and luckiest test subj- I mean volunteer to help him determine their effectiveness.
*Dr. Trottlestein and related parties reserve the right to deny all wrongdoing in the event that testing is proved to be inhumane or be in contravention of the World Peace Bill.
Alone - or with friends - you must fight your way through waves of these creatures in environments specially created by the good doktor to test how well they'd do in helping him take over the world! Survive it all, and the Dr. has promised you your freedom...