Since the beginning of time itself, the League of Time Travelers has maintained the approved timeline (ATL). However, Emmett, a former member of the League, and his team of rebels, now threaten all that has been accomplished as they create an alternate timeline that may annihilate the very fabric of space-time itself. The Core has ordered its Wayfarer Time Travelers to find Emmett before it is too late, but one of their own has been captured, and it appears that their ranks may have already been infiltrated. Have travelers from an alternate timeline found a way to come to the ATL? Things have never been more challenging for Ben, George, Athena, and the rest, but business as usual must somehow be maintained. Timeline missions to preserve history have not ceased: Eleanor Roosevelt needs to fulfill her role as global ambassador, and Nora Baker must join the French resistance. Through it all, Agnes's never-ending continuing education classes (with time slips, wormholes, and multiverse timelines) continue.