'Alphas' casting: Summer Glau returns; guest lineup includes Sean Astin, C. Thomas Howell and Lauren Holly

Geek goddess Summer Glau ("Firefly," "Dollhouse") is returning to "Alphas" this season, reprising her role as Skylar Adams for three episodes. Skylar first attracted the attention of the Alphas team (led by star David Strathairn) because, in addition to her wicked highlights, she's a superhuman genius and inventor trying to protect her math prodigy daughter.

Other notable guests on the Syfy hit series' sophomore season include "The Lord of the Rings" trilogy's Sean Astin, C. Thomas Howell ("Southland" and, you know, the '80s) and Lauren Holly ("NCIS").

Bruce Miller ("ER," "Eureka") joins "Alphas" this season as showrunner, taking over the reins from Ira Steven Behr.

Season 2 of "Alphas" premieres Monday, July 23 at 10 p.m. on Syfy.