When the British Parliament creates an award of £20,000 to whoever can come up with a solution for determining longitude at sea, a carpenter-turned-clockmaker, John Harrison, begins his experiments to build an accurate timepiece unaffected by sea travel. His main obstacles are lack of money, a judgment Board convinced that the answer lies in astronomy and not clocks, and the mechanics of the clock itself.

The ever-reliable Ian Hart appears in Part 3 as Harrison's now-adult son and apprentice, and Longitude approaches its dramatic climax with the exhilarating tension of a first-rate thriller. Rallying after sickness to prove the integrity of their marvelous seafaring chronometers, the Harrisons still had to fight for official recognition, and Gould's restoration of the Harrison clockworks provides a fitting coda to this exceptional story about the thrill of discovery and the tenacity of remarkable men.