The Rembrandt Affair by Daniel Silva

Determined to sever his ties with the Office, Gabriel Allon has retreated to the windswept cliffs of Cornwall with his beautiful Venetian-born wife, Chiara. But once again his seclusion is interrupted by a visitor from his tangled past: the endearingly eccentric London art dealer Julian Isherwood. As usual, Isherwood has a problem. And it is one only Gabriel can solve.