Jason has been assigned to guard a train car loaded with poisonous gas with another agent. He's upset to discover that the agent is his enemy, Gregori Nobokov of the KGB, who saved his life in a past mission. As the train starts down the track, the rest of the crew gets Airwolf to scout the trail from the air. Inside the train car, it seems that Nobokov is looking to rehash an old grudge from a mission in Tel Aviv. Due to bad intelligence, Nobokov destroyed a village to kill terrorists, but many innocent women and children were killed as well. He expected Jason to back him up on the mission, but he was against it. He blames Jason for a group of his men being killed in the process. To pass the time, they play a heated game of chess.
While a ground patrol clears a tunnel for the train, they're attacked and killed by Colonel Randolph and his team. Then, they put a decoy train into the tunnel. When a support chopper called "Skywatch" flies over, Randolph waves them on, acting as the original ground patrol. When the train enters the tunnel, it crashes into the decoy train, knocking Jason unconscious. Nobokov thinks it's one of Jason's elaborate tricks, but when Jason comes to, he holds him at bay at gunpoint to get an emergency call out. Unfortunately, the antenna was destroyed in the crash.
Randolph and his soldiers get the decoy train going, with an explosive device installed that will detonate at 50mph. Skywatch sees the train, but nobody responds when they ask for a status report. They alert Airwolf and St. John gets turned around. Randolph orders the door to the train car opened, but Jason refuses, so he has it cut open. Meanwhile, Skywatch and Airwolf continue chasing the now runaway train.
As they continue cutting with the blow torch, the temperature inside the train car rises. Jason explains that the gas in the tanks kills the central nervous system, so it's critical to control the temperature so they don't rupture. As they get close to cutting into the train car, Randolph feels he's doing the country a favor by hijacking the train, as he believes creating the gas was a mistake.
The decoy train has exceeded 50mph, and Mike is about to be lowered onto the train to stop it. Just as Jo sees that there is a bomb on the train, it explodes. When they scan for any sign of life and get a negative return, they all fear the worst.
Randolph's soldiers cut into the train car, and both Jason and Nobokov's guns are trained on them. They eventually have to surrender, and they're taken into a mine shaft while the gas tanks are unloaded. Randolph still wants a key combination to a valve lock inside the train car, and whether or not they refuse, he'll administer a truth drug to force it out of them. Meanwhile, the crew realizes that they chased a decoy train and there's no gas. Skywatch refuses to believe it. St. John goes looking for Jason against Skywatch's orders.
In the tunnel, Jason and Nobokov attempt to escape. Jason pushes Nobokov out of the path of a thrown grenade, but he's still injured by the blast. Randolph injects him with the truth drug so he can get the code when he wakes up. The crew locates the real train and heads in that direction. Now that the drug has taken effect, Randolph talks to Nobokov. In his stupor, he reveals that this mission was his last chance to kill Jason.
Skywatch orders the tunnel to be collapsed to seal in the gas. St. John pretends to agree, but is determined to get Jason out first. They arrive at the mine and St. John goes after Jason. Nobokov gives Randolph his half of the code and passes out, and now he wants Jason's half. This is halted when Mike begins to seal the mountain with missiles. Randolph sends his soldiers to try and shoot Airwolf down. While they're distracted with that, St. John sneaks into the mine.
The soldiers fire four missiles, all of which are destroyed by sunbursts or return fire by Mike. He fires chain guns to eliminate the soldiers. Inside, St. John avoids gunfire from more soldier as he plants an explosive. Jason carries Nobokov out of the mine with St. John as the mine collapses. They're all relieved to know that the gas didn't leak.
A short time later, Jason arranges a final meeting with a now recovered Nobokov before he returns to Russia. They make amends, and Jason gives him a new portable chessboard to replace the one he lost on the train. Nobokov makes the first move, with Jason's move to be made if they cross paths again.