Summer, 1585: As English ships are held captive in Spain, fear mounts of an Invincible Armada, built by King Philip II, and intended to invade English shores. Sir Francis Drake prepares to embark on an expedition by royal commission to cross the Atlantic and seize major Spanish ports, diverting Philip's American treasure supplies to Queen Elizabeth. Giordano Bruno, radical philosopher and spy, accompanies his friend Sir Philip Sidney to Plymouth to oversee Drake's departure.
Unbeknownst to Bruno, Sidney intends to join the mission - and he wants Bruno to go too. But when a ship captain is brutally murdered, and Drake's life threatened, it becomes clear that someone plans to destroy the expedition before it begins. Bruno and Sidney hunt for the killer, but are they being lured into a trap? And when Drake's young wife and her cousin arrive, Bruno and Sidney find themselves thrown into an unexpected rivalry.