What's next for Alex Trebek in his fight for his life. Inside the "Jeopardy" host's history of health problems and how his chemo treatments will affect the show. Then, Jason Priestly breaks his silence on the death of his longtime friend, Luke Perry. What you never knew about the "90210" stars' unbreakable bond. Then, R. Kelly back in jail after his blowup with Gayle King! But was it all an act? Plus, is Chris Pratt joining "The Masked Singer?" What he's telling ET! And, Chris Evans shows off his new pet project! Entertainment Begins and Ends with ET!