Time Traveler

There are three cells that we know of in London. They are all inspired by a Russian revolutionary named Boris who has set up the cells to be separate so that the compromise of one will not threaten the others. We have a spy in one cell and he obtained some of their enciphered messages. He showed us how the cipher system works. Unfortunately, they discovered him and killed him, so he cannot help us now. The messages are usually short and tell others where and when to meet, but each cell has its own keyword. This man is not part of that cell, so we don't know his cipher key.