When King Triton's trident enters the Isle of the Lost, Mal, Evie, Carlos, and Jay devise a plan to find the magical object before Mal's wicked rival Uma can get her hands on it.

Conor, Abeke, Meilin, and Rollan are prisoners. Framed for a crime they didn't commit, the four young Greencloaks have been captured by the ruthless Oathbound. Rather than facing trial with the rest of their order, the friends and their spirit animals find themselves smuggled to a remote palace. There they discover that the plot against them runs deeper -- and is far more sinister -- than anyone realized. Someone has been manipulating both the Greencloaks...

The Super Sidekicks just saved the world! And now they've been invited to join HERO: The Heroic Earth Righteousness Organization. It's the most exclusive club for the planet's most famous superheroes. (No big deal!) But before they can become members, they must pass the hardest challenge in the universe--a test so scary only the truly heroic can survive.