Ep 18. Mutant Gangland

As the title implies, "Mutant Gangland" initiates with the revelation of a new gang that holds sway over the city, made up completely of mutants. The turtles try to keep their existence secret to avoid conflict, but when the Shredder determines to take out the gang, they cannot stand aside. In the meantime, Casey Jones attempts to get back into the fight, but with his absence from the action for a long time, he may have lost the touch that made him an asset before.

The episode begins with the Turtles investigating the theft of a strange component from a tech company. The component is vital, and its loss is influencing the company's capacity to generate revenue. Mikey figures out that the robbers were MUTANT ROSHI and his gang, who have never been heard of by the turtles before. Roshi has four of his men with particular mutations that make them especially hazardous: a giant snake, a bear-man, a four-armed anteater, and a dragonfly woman.

Later, Leo investigates a niche in an alley and discovers a door that leads down to some type of mutant bar. He realizes that the Mutant Gang resides here and is reluctant to go in because he thinks they are going to immediately start a fight with whoever they see.

When he ultimately enters the bar, he's amazed to see that it's just a regular bar, full of mutants from all over the world. Everyone appears to be having a good time, just as he hoped. Roshi emerges from the back and serves beverages behind the bar. He sees Leo and acknowledges him but appears to be uninterested in pursuing a conflict. Before departing, Leo hands Roshi a note telling him that he had taken the component and asking him to stop thieving.

Back at the lair, the turtles wonder what to do next. Donnie, Leo, and Raph want to collect the component away from Roshi and his men, while Mikey advises leaving it alone and letting the Mutants have it. Master Splinter enters and reminds the Turtles that they are in no place to be dictating who gets to keep what. He advises against any simple confrontations with the Mutant Gang and leaving diplomacy to be handled by the authorities whenever feasible.

Casey Jones arrives at the lair, prepared to assist, but Mikey blows him off sarcastically. Jones asks the team what they're working on, and they tell him about the component theft and the Mutant Gang. He declares that he and the turtles defeated the Purple Dragons and proposes that they tackle the Mutants now. However, the turtles remind him that he's been out of the game for a while, and they're not sure if he'd be such an asset to their team anymore.

Casey leaves angrily, and the Turtles keep an eye on Roshi and his squad. During one of their heists, the Foot Clan captures them, and they get taken to Shredder's hideout. Shredder advises Honano that he has no quarrel with him or his gang and decimates his squad; nevertheless, he declares that whoever continues to steal from him will have to face the consequences.

In the conclusion, the turtles team up with the Mutant Gang to defeat the Foot. However, they do end up losing some of their members to the foot.

Without a doubt, episode 18 of season 4 of Teenage Mutant Ninja Turtles is an action-packed spectacular episode, featuring the clash between the Turtles and Roshi's Mutant Gang. Mutant Gangland raises the stakes and sets vital plot points for future episodes, making it easily one of the best episodes of the season.