Harry Potter is coming to an end, and the movies are only two books behind, so no wonder Warner Brothers is making sure to line up what it thinks will be its next big franchise. And according to the Hollywood Reporter, the movie studio thinks it has found it after picking up the rights to another seven-book children’s fantasy series, SEPTIMUS HEAP. HarperCollins Childrens Books publishes the internationally bestselling series in the US.

Written by U.K. author Angie Sage, the series revolves around two babies who are switched at birth: one a boy who discovers his birthright as the seventh son of a seventh son, and who is destined to become a powerful wizard; the other a girl who is fated to become a princess. So far, three books have been published — MAGYK, FLYTE and PHYSIK — which have become bestselling books for their clever use of charms and potions as well as for their sense of humor. “Septimus Heap: Magyk” will be produced by Karen Rosenfelt (“The Devil Wears Prada”) with author Sage as executive producer.