When Labor accidents begin to rise around Tokyo Bay, detectives Kusumi and Hata are dispatched to investigate. Their inquiry uncovers a web of government cover‑ups and a conspiracy involving a new biological weapon called WXIII‑Wasted Thirteen, as well as a personal link to Hata. The only way to halt the threat is to ally with the military and command WXIII into a confrontation with the Labors of Special Vehicle Division 2. This film serves as a side story set between Patlabor Movie 1 and Movie 2.