It Lives in the Sewers

S1 E22: Betty is spooked in the middle of the night when she hears strange noises in her house. Archie eventually narrows down the source as coming from the plumbing and they learn that something is alive in the sewers of Riverdale. It turns out that Jughead's pet baby alligator got flushed down by mistake and is now feeding on a discarded barrel of toxic waste. The baby croc has become a dangerous mutated beast and it's up to Archie and the gang to stop him before Riverdale citizens become a target for lunch!