At 6:29 p.m. on October 31 in Maryland, America, a little boy named Alex draws his last breath while still dressed in his Halloween costume. At 12:25 a.m. on the same day in Saxony, Germany, Rite Auer is a child of similar age to Alex who dies alongside him. These two are "twin souls,'' destined to meet before they pass on to the other side.

As they travel toward one another, Alex and Rite's souls are strangely drawn in the direction of a few compatible people who are able to see, hear, and interact with them. Alex comes across Haruhi Kurahashi, a woman with a twin sister who sees Haruhi as a rival. On the other side of the world, Rite meets a former doctor by the name of Theo Kloden who currently runs a small homemade jewelry business.

The fateful encounters of Alex and Rite with Haruhi, Theo, and others allow them to recover the memories of their past lives and reasons for their deaths as they gradually close the distance between each other.