Thirty years after the shocking and never-solved 1986 assassination of Swedish Prime Minister Olof Palme on a snowy street in Stockholm, an activist priest is found gruesomely sacrificed on the altar of a Swedish-American church in Minneapolis. The church's immigrant janitor is also slain, execution style. The crime shocks Hennepin Island, the church's time-forgotten riverfront neighborhood, where Span Lokken, a demoralized newspaperman and his improbable partner, Maggie Lindberg, the murdered clergyman's stylish young assistant, join forces to search for the killers. The trail leads to the castle fortress of the island's reclusive kingpin, Jonas Kron, whose "lost colony" delusions hide a gripping international mystery that brings the story full circle. Along the way, the curious bond between the unlikely detectives - Span and Maggie - only deepens as they seek to fill the empty spaces in their own lives.