Realizing that the Turtles somehow know his warriors' every move, the Dragon Lord decides to set a trap for the TMNT by sending his five strongest Rank to the Bronx Zoo for an ambush. The vile reptile augments his soldiers' formidable strength with the last five doses of the Serum of Invincibility. The Turtles, meanwhile, having analyzed a sample of the serum taken from the previous battle with the Rank, are righteously angered when they discover that the substance is composed of powdered rhino horn, tiger bone and turtle shell! With both sides fired up, the next confrontation at the Zoo is long and furious, a true-life death struggle. As the battle progresses, the TMNT discover that the serum is but a placebo, having no real invincibility power other than to make the user think that he is invulnerable and thus overcome his fears. With this knowledge, the Turtles hand the Dragon Lord and his minions a most crippling defeat! Also, the simmering differences of opinion between Leonardo and Raphael reach a climax, as the Turtles realize that while their differences set them apart, it also makes them the same... as pieces of the same puzzle. And moreso: as turtles they are part of an ancient tapestry of life, of a lineage stretching back to the age of the dinosaurs. Above all, turtles are survivors... and there is much wisdom in survival.