When Pat and Jen tumble into the underworld while searching for their pet, Bomby, they don't expect to end up on an adventure with a unicorn called Gizmo, the mysterious Mr.Rainbow and a rude boater who goes by the name "Captain Cookie"- but that's exactly what happens. Can Pat and Jen find Bomby and flee the underworld before they get zombified by the evilest villain of them all-Evil Jen?