You can't program love-or can you?

Kayleigh Renshaw has come up with the idea for a brilliant "compatibility app," a new kind of matchmaking software. All she needs is a programmer to help her bring the idea to market-and she knows exactly who she wants. But Niall Walsh—a code whiz and her former best friend—has been avoiding her since he returned from Afghanistan. In spite of their history, and some sparks that go beyond friendship, he's proving reluctant. Is it her, or is something darker holding him back?