First of all, I want to thank everybody who sent suggestions for stories. Some of them were perfect for the kind of story I have in mind. The major point is that I want both Bill and Sally to figure significantly in the story. That means that some of the suggestions won't work unless I can come up with a twist that will let both of them play.
Currently, I am working on a story called "Time-Walking, The Silk Road." the Silk Road was the overland trade route between Europe and China, and it existed from Roman times up until around the 14th or 15th Century. My story centers on the part between Antioch and Samarkand in the 2nd Century AD. This is more of a violent story set between the caravans and the bandits that plagued them than was the first Time-Walking story.
The story makes a strong use of the crossbow, and I am sure that some people will claim that is impossible. However, remember that the crossbow was invented in China prior to 300 BC, and the Silk Road's purpose was to enable trade between China and the West. In other words, be damned sure that you check before you dismiss something as an anachronism.
This could be a long-running series if readers support it. Thanks for your help and interest so far. Oh, by the way, the level of sex in the series is going to bounce up and down (pun intended).