Barney begs Ted to continue seeing his much younger, much wilder girlfriend, even though Ted has nothing in common with her. Meanwhile, Robin must adjust to the power of the bling.

The brothers deduce a witch is sacrificing people to summon a dangerous demon. Robert Wisdom ("The Wire," "Prison Break") guest stars as Uriel, a specialist angel.

When Seth visits Summer at Brown, he finds an empty dorm room. Meanwhile, Sandy and Kirsten take advantage of an opportunity to bond with Ryan, who is in a Taylor-induced haze, Kaitlin meets the mean girl of Harbour School and tries to best her by throwing a huge party at the Roberts house, and Julie learns that Newmatch is more than just a dating service. Elsewhere, the truth about Che comes out.

As the team investigates a bomb explosion that killed a 17-year-old girl in a clothing store dressing room, Horatio discovers that Julia Winston and Kyle are facing new troubles.

Zoe confides in Ruthie, but when Martin ends their relationship, she thinks Ruthie betrayed her confidence and Eric and Annie suspect that Sam and David are feigning illness so they can stay up late and eat sweets.