Billy and Mandy are a mismatched pair of youngsters who befriend the Grim Reaper after winning a limbo contest against him. Since the Grim Reaper lost, he has to be their friend, and the three go on adventures together. Between school, family and visitors from the spirit world, Billy and Mandy sometimes need help to clean up the messes they get themselves into, and that's where Hos Delgado comes in. Hos and the Grim Reaper are not friends, and with Mandy's bossy nature and Billy's curious attitude funny escapades ensue.
When the Boogey Man causes Grim to lose his powers, rank, and title in the Underworld Court for misusing his powers, he plots to seek out Horror's Hand and take over the world. It's up to Billy, Mandy, Irwin, and Grim to get to Horror's Hand before the Boogey Man does.
The Spider Queen wants to take revenge on Grim for denying her the rightful place as the Ripper.
Irwin, Hoss Delgado, Jeff the Spider, Fred Fredburger, and General Skarr from the "Grim Adventures of Billy and Mandy" team up to fight an evil candy army from the Underworld on Halloween.
