On Halloween night, a mustachioed man visits April, expressing interest in a rather unusual item: a hideous six-armed idol. But the statue is no ordinary junkshop knickknack; it can be used to invoke a horde of imps that proceed to clean out the city and bring its spoils to their master, a criminal who calls himself The King of Thieves.

When the President of the United States arrives in New York City, an invasion of what seems to be aliens attacks at the most inconvenient time. However, the Turtles investigate this "invasion" and find out that Bishop is behind it. The question is - why?