In chess a Dubious Move is a move that may be considered a mistake, like Fam's plan to hijack the Sylvius. Fam plans to steal the infamous ghost battleship, the Silvius for Millia to regain her kingdom. After discussing what type of ship the Silvius is with Dio and Giselle, they conclude the ship is a hit and run aircraft carrier. On the day of the operation, Fam, Giselle and several Vespa pilots ride off to the Silvius with Millia and Teddy tagging along on Dio's vanship. After tricking the Silvius to head into a valley, Fam gives a message to the crew of the Silvius to surrender. But the Silvius, commanded by Tatiana and her executive officer Alister, ignores Fam's message and moved on. Fam and the Sky Pirates try to stop the ship using various tricks but none of them work on the Silvius which at one point Tatiana herself chases off Fam and Giselle with her red vanship while her vanship pilots capture Fam's crew. With the Silvius escaping to the Grand Lake, Fam and Giselle take a desperate gamble by sneaking into the Silvius but realize too late to learn that the room they just enter was a waterlock, revealing the Silvius is also a submersible ship. Fam and Giselle are brought to the bridge to meet Tatiana and Alister where Tatiana ridicules Fam for trying to steal the Silvius. Nevertheless, Tatiana offers to free Fam and Giselle if she helps the Silvius steal 15 Ades battleships intact. Fam accepts her offer after Tatiana mocks Fam that she can't do it, just as Dio, Millia and Teddy arrive at the bridge.