Past and present collide on the high seas when Clare and Allie hurtle back in time once more in a perilous attempt to retrieve Marcus Donatus—Allie’s blast-from-the-past crush—and put an end, once and for all, to the Time Monkey Shenanigans. But when Clare and Allie unexpectedly find themselves temporal stowaways on a Roman warship full of looted Celtic gold, sailing straight for the heart of a magic-fuelled maelstrom, there’s not much they can do but hang on for the ride—and hope Milo can tap into the Druid lore trapped in his genius brain to help bring them home, before it’s too late. The only thing that’s going to save Clarinet Reid and Allie McAllister now is if they join forces with old enemies, new loves … and unexpected friends.