A phantom thief named Rusty Nail sends a letter to a mansion and threatens to steal its treasure, so the Mikuni Detective Agency is called in to protect it.

The gang decides to seek a medical professional for Masamune's wounds and are greeted by a suspicious-looking doctor and a little girl.

The gang takes the job from Ozu to go save Dorothy and find themselves in an underground lair filled with traps.

The team randomly runs into Rusty Nail at a supermarket, who declares that she will get back at them for ruining her last job by stealing something from their agency.