Elspeth Gordie leaves Obernewtyn to testify at the trial of a rebel traitor, but instead, she finds herself enmeshed in an invasion. In seeking to thwart it, she is swept into the strangest and most dangerous journey she had ever undertaken; a journey which brings her to the mysterious Herder Isle and to the Council occupied West Land, where she must find a deadly plague carrier. Elspeth feels that she has strayed far from her quest to find and disarm the weaponmachines that destroyed the Beforetime, but as ever, she discovers that everything she had done had brought her to the final clue she will need in order to reach the weaponmachines.