After such a lighthearted previous issue, Haney and Cardy deliver the darkest story yet for this book, in Teen Titans 14 (March/April 1968).
The story has a weird and moody opening, with the Gargoyle confronting Robin in a graveyard, getting him to shed his costume, and his identity.
The story then jumps backwards to explain how this all came about. The Gargoyle claims to be a person wrongly imprisoned by one of the Teen Titans. This is, technically, the first appearance of the character, although much later it would be retconned that the Gargoyle is the same person as Brom Stikk, Mr. Twister, who Robin, Kid Flash and Aqualad fought in their first outing. So while the identity of the falsely imprisoned Gargoyle is never revealed, one can assume that this is Mr. Twister, claiming that his incarceration was unjust.
At any rate, the Gargoyle draws the heroes to him, and then makes them all suspicious of each other, stating that only one of them is guilty of being the "bad" one who went after him, and promising freedom to the other members if they will turn against Robin, who the Gargoyle basically accuses. Kid Flash, Aqualad and Wonder Girl all begin to doubt Robin, which gives the Gargoyle enough power to shunt them all into Limbo. The Gargoyle wears a special ring which allows him to freely travel in and out of that realm.
Once in Limbo, the Gargoyle can control the corrupted Titans, and he uses them against Robin, all the while playing his twisted mind games, trying to get Robin to give up being a hero. It's such a different story than anything that has come before, far more devious and emotional.
Robin manages to destroy the Gargoyle's ring, which traps him in Limbo and, for reasons that are far from clear, releases everyone else from it. It's worth noting the tornado effect when the Gargoyle loses control - pretty much the same effect that Mr. Twister could create.
Only Robin winds up will a full memory of the events in this story. Wonder Girl comments that this is the first time she has seen him without his mask, which makes it clear that, at this point, the Teen Titans still did not know each other's identities.
The Gargoyle returns three years down the road.