Before Gabriel is able to make Sarah his mate, he is called away for months to complete some specialized training as a Hunter.  To be a Hunter is a huge honor and Gabe feels that Sarah will be ok waiting, as they always have their dreams.  Add to that he is concerned about the sexual demands he dreams of making on her and he thinks the time apart will help them both.  In fact, he befriends another shifter, Chloe, before he goes so that she will have someone to talk with about him being gone.  What he doesn't count on is that person not sharing the information with Sarah.