Timecracks act as portals to other dimensions. They have existed since the creation of time, and when one arrives during a storm at the newly discovered pyramid site in the Yucatan jungle, it's the beginning of a nightmare journey into another world for archaeologist, Malcolm Kinross and his wife, Lucy.
And when another timecrack strikes the secretive energy facility in New Mexico, their sons, Archie and Richard, along with their tutor, Marjorie, and their uncle, Professor John Strawbridge, all find themselves thrust into the same world of New Arrivals, ancient warring tribes and deadly enemies.