Even Baxter might be changing his mind on this. He and Molly seem to have reached a sort of detente. They take turns chasing each other---no hissing---and then Molly retreats to the basement and Baxter remains upstairs.
Yesterday, Baxter had pretty much stopped hissing; instead he just ignored Molly's presence. I see nothing. Today he is paying much more attention. I think that Molly is having fun but I don't know what Baxter's take is on all of this running around.
I am assured by everyone with experience in bringing a new cat into a home with a resident cat that this will all work out, that they will end up snuggling up together to sleep.
Again, I'll believe that when I see it.