Two eleven-year-old misfits try to solve the mystery of a dead magician and stop the evil Dr. L and Ms. Mauvais, who are searching for the secret of immortality.

The Tuck family is confronted with an agonizing situation when they discover that a ten-year-old girl and a malicious stranger now share their secret about a spring whose water prevents one from ever growing any older.

"Citra and Rowan have disappeared. Endura is gone. It seems like nothing stands between Scythe Goddard and absolute dominion over the world scythedom. With the silence of the Thunderhead and the reverberations of the Great Resonance still shaking the earth to its core, the question remains: Is there anyone left who can stop him? The answer lies in the Tone, the Toll, and the Thunder." -- Provided by publisher.