"Keizoku," unfolds in the present, beginning in the dimly lit basement office of the Metropolitan Police Office's Criminal Investigations Section One, which is charged with pursuing "pending" (keizoku) investigations -- i.e., cases that everyone else has given up on.
Nanami Kirishima is anxious to solve the mystery surrounding the deaths of her mother and her father, who perished in a shipwreck 15 years ago.
Now Nanami has invited the survivors to a reunion on the tiny island she calls home and, conveniently, they have all accepted.