Nita beams at the thanking-the-Bar, and pours herself a cup of tea, two sugars. "Okay. It's probably easiest to start with the multiple universes thing. There's some theories that say that when something happens that could go two ways, two universes are formed. Like. . ." She casts a glance over Mary's attire. "Like the Battle of Waterloo. In some worlds, Napoleon won -- in some, he lost. With me so far?"