The Red Scrolls of Magic - The Eldest Curses 1 (Broché)

A lavish trip across Europe with Alec Lightwood, the Shadowhunter who, against all odds, is finally his boyfriend. It doesn't seem like too much for the centuries-old High Warlock to ask for. But no sooner have they settled in Paris than an old friend arrives with news about a demon-worshipping cult called the Crimson Hand that is bent on causing chaos around the world. A cult that was apparently founded by Magnus himself.
Years ago. As a joke. Now Magnus and Alec must race across Europe to track down the Crimson Hand and its elusive new leader before the cult can came any more damage. As their quest for answers becomes increasingly dire, Magnus and Alec have to trust each other more than ever — even if it means revealing the secrets they've both been keeping.