Buddies Lem and Mags, the con men stars of We Are Not Good People, return in Last Best Day in a gripping race against time. After Lem is taken hostage by a powerful mage, Mags find himself abandoned and abused by people he had once thought were friends. Without his partner in crime, he consistently loses control of his dangerous temper, leaving a trail of new enemies behind him.

With no other choice but to cast a dangerous and potentially life-changing spell with blood magic, Mags attempts to track down Lem and keep them both safe. But all magic comes with a price, and Lem and Mags face the most perilous challenge of their lives.