What surprising twist does the story take with regard to Remy, and how might it change future events?

The story takes a surprising twist when Remy is discovered to be working for the Teacher, Fache. Remy frees Silas and they go after Sophie, Langdon, and Teabing in the church in order to retrieve the keystone. The author brings an added dimension of distrust to the story. When Remy betrays Sophie, Langdon and Teabing, it's unclear how he came to be in the Teacher's employ. So, it makes everyone's motives questionable, especially Teabing's, since they were in a house together for an unknown amount of time.