In 1674 England, Snowy and Minty oversee the building of their ship, The Gillfish 2, after sacrificing the original Gillfish while battling dastardly Captain Percival Savage. In The Secret Message, the sequel to Starry Night Surprise, Snowy designs special features such as steam thrusters, wing-like sails, and Kotter cannons. While the crew works, they cross Epping Forest to visit the orphanage and meet Goldie, a sweet girl with a penchant for racing everywhere and the inability to lie.
Meanwhile, Captain Savage has resurfaced, desperate for revenge. He encounters a group of men willing to join the G2 crew as his spies. Savage vows to pay whatever it costs in his quest for retribution.
As First Mate Carter shows Snowy and Minty around the nearly complete G2, a message arrives from John Flamsteed, the royal astronomer, requesting their presence at Greenwich to meet Sir Christopher Wren. In London, they also meet Heinrich von Brock, a telescope maker from Germany, who will make a telescope for Snowy's cottage.
When Snowy and Minty return to the orphanage, they learn that Goldie is gone. And the girls get the feeling something's not right. But before they can act, a mysterious ship attacks The G2. As cannonballs fly, a tense, dangerous battle erupts. The girls must use every technical weapon they have, combined with precision timing, heroic deeds, old-fashioned ingenuity, and a little divine intervention before sending Captain Savage to meet his fate.
Finally settled in Epping, Snowy's telescope arrives. As she and Minty put it together, she finds a mysterious note from Goldie on the lens.
