After SpongeBob's pet Gary starts biting everyone, a rumor spreads through town that he has a rare snail disease, and as the Snail Bite panic builds, everyone's zombie-like behavior leads to a manhunt for Gary.
When Mr. Krabs gives SpongeBob the only key to the vault holding the Krabby Patty's secret recipe, SpongeBob and Patrick must keep it safe, until it is stolen by a passenger on their train.