Captain Pryde and the Marauders have vowed to save Threshold and all its mutants, no matter the odds. But maybe they should’ve checked those odds first! Witness the origins of Threshold and of mutantkind itself! And fight to protect those origins as the Marauders find they’re not the only castaways from the future to take root in the deep past. All this…and the first appearance of GROVE, without whom the Krakoan era wouldn’t exist!