The Seal has been lost ever since the mysterious woman who rescued Elyon as a baby used it to create a portal and escape. While hiding from Lurdens in the sewers, Blunk finds an amulet to add to his junk collection, which turns out to be the Seal of Phobos. Unknowingly, he creates many portals while strolling around Heatherfield. Meanwhile W.I.T.C.H. are at a rollerskating race. They find the portals when Irma crashes uncontrollably through bushes. Back in Meridian, Caleb is trying to evade a search party, but is trapped when all the portals created by Blunk are closed by the Heart of Kandrakar. Cedric is gaining on him. When the girls find Blunk, unforeseen circumstances lead to the merging of the two magical items. W.I.T.C.H. uses the Heart's new ability to open portals to save Caleb. Will then uses the Heart and the Seal of Phobos to open the Book of Secrets, and everybody finds out Phobos' plan.

Caleb learns that Elyon's adoptive parents, the Browns, are being held in the forbidding underground prison at Cavigor. He and the Guardians plot a difficult escape: while a distraction from above draws guards upwards, Cornelia will tunnel in from the Infinite City below. But one slip and Phobos will discover the rebels' secret subterranean hideout.

When Caleb's best friend Aldarn accidentally becomes hypnotized by Elyon and agrees to sign a peace treaty, Caleb has to fight him for the position of leader. Meanwhile, after leaving their baking duties for the school bake sale to Blunk, the Guardians enter a trap filled with Larveks and they must defeat them before the rebels get eaten.