CBS has released their official summary for “The 43 Peculiarity,” which hints at subterfuge, insecurity, and attractive guest-stars.

The cast of The Big Bang Theory seem to be coming down with a bad case of suspicion (sure, that’s a disease) in “The 43 Peculiarity.” The official description says:

Howard and Raj try to get to the bottom of why Sheldon disappears every afternoon at 2:45. Meanwhile, Leonard and Penny deal with jealousy in their relationship.

Also revealed are the two actors set to guest star in “The 43 Peculiarity,” which suggests the origin of Leonard and Penny’s relationship tension. Margo Harshman is set to reprise her role as Alex, Sheldon’s attractive assistant, whose friendliness with Leonard made Penny uncomfortable earlier in the season.

On Penny’s side of the jealousy-equation, Ryan Cartwright will appear as Cole, a new friend of Penny’s who will spark suspicion in Leonard. It is assumed that Penny and Cole meet in Penny’s community college class; of course, Leonard’s misguided support of Penny’s educational aspirations was a source of friction between them in last week’s episode.

As for Sheldon’s suspicious weekly disappearance, we can’t imagine where he might be going. (Perhaps to a galaxy far, far away? On a train?) But no matter what, it will be wonderful to see Raj and Howard bro-ing it up again like old times.

This week, tune in to “The Habitation Configuration,” airing at 8 p.m., and check out a promo and new pictures in the meantime. The official description from CBS says:

Wolowitz struggles with moving out of his mother’s house. Meanwhile, Sheldon is caught in the middle of an argument between Amy and Wil Wheaton.