Team Venture, Conjectural Technologies and the Order of the Triad come together as Dean and Hank prepare to face an obstacle that is more intimidating then anything they have confronted before: a prom to celebrate their "graduating" high school, while Dr. Venture throws out all the stops to bring the twins the best dance $500 can buy. But when things go awry, the greatest battle in Venture history looms as two old enemies - the OSI and SPHINX - clash once again.