Mars is under siege! Just before Halloween 2071, a terrorist bomb destroys a tanker truck on Highway One, close to a densely-populated crater city.

There are casualties up to half a mile from the blast — 500 killed or injured by what appears to be a biochemical weapon. The reward for the bomber's capture is a massive 300,000,000 woolongs... and there are four humans and a dog who really need the money. Down on their luck as usual, the crew of the Bebop get on the case.