Mysteries Unlimited Ltd is the name of a small company that answers questions of any kind, no matter how strange or even dangerous. Occasionally they take projects that cause even the redoubtable owner and Willie Nelson, look alike Sydney Constant Lee to take pause.
Mysteries Unlimited is staffed by a zany bunch of misfits, all of whom have one thing in common; they are very smart. However they don't always operate in close proximity with reality. The May Day Massacre, as the theft of 90 million dollars from a San Francisco bank was called, is just one such mystery.
Miss Jean Heely, an officer of the bank is accused of the theft and incarcerated for the crime. She solicits the help of Mysteries Unlimited and we get to follow Sydney and his strange band as they solve the mystery and get her out of prison.
Before this happens they will confront crooked FBI agents, a senior member of the bank's management, a demented bank employee and a Japanese Yakusa mobster who takes a personal dislike to Sydney Lee.