'House's' Robert Sean Leonard and 'ER's' Gloria Reuben join 'Falling Skies'

Robert Sean Leonard, who rode away into the sunset with Hugh Laurie in the "House" series finale, is joining TNT's "Falling Skies," Deadline reports.

In a five-episode arc, Leonard will play Roger Kadar, aka the Rat King, "an obsessive but gifted scientist who runs Charleston's power grid and lives underground with his pet rats."

Gloria Reuben, star Noah Wyle's former "ER" colleague, will also appear in five episodes of the sci-fi drama's third season. She'll play Marina Perlata, a politically savvy aide to alien resistance leader Tom Mason (Wyle). Reuben previously appeared in TNT's legal drama "Raising the Bar."

"Falling Skies'" second-season finale aired Aug. 19; it is scheduled to return in 2013.