From the looks of it,the episode is when Van Kleiss comes back but something chases him.
My guess is either Providence with Black Night chases him,or something else does. Also,if Rex sees Van Kleiss is back Van Kleiss will talk with Rex about a few things,they will have a fight,or it will show some history on Rex,Van Kleiss,Caesar,or it is a different kind of history that a time machine would take you,like 1800's or something that is compaired to the saying,"history." It may also have to do with timing. Like a timer ,a clock or some magic time thingy.
Also,if you remember the picture of Van Kleiss,probably stuck in it. Black Night may be the one to bring him back. There is no telling until it comes on.
Tell me what you think and comment.