Tracy finds a chemist being held as a slave by Yogee Yamma in an abandoned section of the subway. After Tracy prevents Yogee from killing the man, Yogee escapes and traps the other two in the tunnel, which fills with water. A street cave-in lets Tracy and the chemist escape.; In a drunken stupor after getting a $500,000 payoff and thinking he has gotten rid of Tracy and the chemist, Yogee Yamma passes out in a hotel room. He forgets that the nerve gas he carries has to be kept cool with dry ice and the device explodes, filling the room with flames and killing him. Later Tracy investigates a bomb and he and Pat are captured by Pearl Erad, the Black Pearl.; Black Pearl takes Tracy and Patton to a secret proving grounds in the mountains to have them test her combination tank-plane-submarine. During underwater tests, Tracy finds a way to use an aqueduct to send a message for help.; Tracy and Patton have to test the tank against flame-throwers. The police interrupt the test but have to deal with the flame-thrower themselves. Pearl and Horace escape to an underground hangar with a foreign dignitary, but are stopped when the diplomat proves to be a G-Man in disguise. Later Junior goes into business with a man named Buck, parking bicycles on his vacant lot.; Junior sets up a bike-parking business with a man named Buck. On his first day of business, a truck intentionally backs over the bike racks and Junior is left to find a way to repair or replace the damaged bikes. Deafy Sweetfellow contacts Junior with an offer to supply him with replacement bikes at very low prices. Junior starts selling the bikes, but one of the boys' fathers accuses him of selling stolen bikes.; Junior tracks the bicycle thieves to their mobile workshop, but the crooks back the truck suddenly, severely injuring him. Dick Tracy returns from a vacation two days later and finds Junior in the hospital. The thieves are stopped by a motorcycle policeman and shoot the cop and abandon the truck. Deafy and Buck go to Buck's mother's hamburger stand to hide out.; Tracy and Patton capture Deafy's gang at his mother's hamburger stand, but Deafy escapes. Deafy is sprayed by a skunk and Tracy captures him when he tries to hide in a load of Christmas trees.