...the book scene. He mentions the dagger, which freaks Joffrey out, and then explicitly asks Sansa (it's her POV chapter) about knowing what happened to Bran after he got pushed out of the window.

Jamie later also figures it out during another meeting with Cersei (their first since "the scene") after she mentions that Robert had said that it we have been better to put Bran out of his misery while in front of Joffrey and the other kids.

Don't know if they can pull off the later scene, especially after their "interpretation" of the tryst in the Sept (in the book, Cersei makes another pass at Jamie), but I guess it's possible.