Inside the Foot Genetics Lab, the Turtles learn of past experiments that turned human subjects into monsters. The brothers soon encounter a group of these creatures who are at first hostile, but eventually become allies. The Turtles now find themselves helping these creatures evade the attacks of similar, but mindless monsters. This new partnership takes the Turtles deeper into the seemingly haunted catacombs, where creatures, and now Donatello, have disappeared.