Harley Quinn joins forces with a singer, an assassin and a police detective to help a young girl who had a hit placed on her after she stole a rare diamond from a crime lord.
In the year 2035, convict James Cole reluctantly volunteers to be sent back in time to discover the origin of a deadly virus that wiped out nearly all of the earth's population and forced the survivors into underground communities. But when Cole is mistakenly sent to 1990 instead of 1996, he's arrested and locked up in a mental hospital. There he meets psychiatrist Dr. Kathryn Railly and the son of a famous virus expert who may hold the key to the Army of the 12 Monkeys; thought to be responsible for unleashing the killer disease.
When the Mystery Inc. gang is invited to Spooky Island, a popular amusement park, they soon discover that the attractions aren't the only things that are spooky. Strange things are happening, and it's up to Scooby, Shaggy, Fred, Daphne, and Velma to uncover the truth behind the mysterious happenings.
