Sheldon's latest scientific breakthrough makes him feel like a fraud – and threatens to haunt him forever. Meanwhile, Howard's romantic gesture to Bernadette causes Penny to step up her game with Leonard.
Tim and Jill comfort Al when his mother dies; a new producer makes Tim's job at "Tool Time" very unpleasant.
When Kat winds up getting sick just days before her favorite local TV newsman plans a visit to the café, she turns in to her alter ego, Katzilla. Meanwhile, after Randi lands her dream apartment, Max starts trying to find his own.