it occurred to me that there´s a pretty obvious parallel between the hallucination scene in 2x03 and the last scene between Scott, Kate, and Seth in 3x04.
In that both times, Seth thinks there´s no way, he could possibly get Kate back, only to suddenly realize she is back, in 2x03 she is obviously not actually back, but regardless of that. But in the case, of the scene in 2x03, it starts with “Kate” gently caressing his face, telling him she couldn´t leave him, until suddenly she turns his head, and she turns into a culebra trying to attack him. In the scene in 3x04, it is Kate, actual Kate, begging him to shoot her, but as soon as he tries to touch her, Amaru comes back and attacks him.
In both cases, he lets himself believe that she is back, even though he thought he´d lost her for good, only to have ripped it away from him a moment later. Only in 3x04, it is so much worse, because this time it´s real.