The Messenger (Book Two of the Timeless Trilogy)

Ben is adjusting to his new life amongst the nomads of the Asian Steppe, but he can never forget why he is here in the first place. He manages to persuade his Guardian Angel, Harry, to find a way to get word back to Sam that he is alive but in another time. Harry hasn't been to London before; it's not often that angels get back to visit Earth, and it all looks to be for nothing when Sam is being evicted from her home for being behind with her rent.
What's more, she wants nothing more to do with him. Harry can't just come out and tell her he is an Angel, but Ben told him to give his letter to Sam no matter what. Time for Plan B. Meanwhile, Ben has more on his hands than he knows what to do with. On the run from his adopted tribe and cheating death on more than one occasion, he decides to end his days on a remote farmstead. However, Mandana who helps run the farm with her father is determined to nurse him back to health.
Just when Ben thinks he has finally made himself a family and a home that he always wanted, a face from the past returns with awful consequences.