Transformers: Prime/Recap/S1/E09 Convoy

The Autobots get an angry call from Fowler. His plane's been shot down while transporting the hi-tech Dynamic Nuclear Generation System. Called the DNGS, pronounced "Dingus", for short, it's a volatile nuclear device, and he needs help in completing his mission. Optimus says that using the Ground Bridge to transport it would be too dangerous, so instead they'll have to take it by road. They soon have it loaded into a semi trailer which Prime starts hauling, with Bulkhead and Bumblebee as an escort. Fowler's disappointed that he doesn't get to drive. Ratchet and the kids monitor the journey from the Autobot base.

Optimus, in vehicle mode, is irritated by Fowler's enthusiasm with the horn in his cab. Unknown to any of them, the convoy is being observed by a helicopter. Fowler and Optimus are discussing whether there was any evil on Earth before the Decepticons came, when they spot the helicopter, which Fowler believes is a Decepticon. Five green sports cars move in on the convoy, but Optimus warns everyone to maintain their cover and stay in vehicle mode. Ratchet's surprised that they're not showing up on his sensors. All is made clear when one of the cars draws level with Optimus’ cab, and a masked human aims a gun at Fowler. Optimus orders the other Autobots to use non-lethal force only. Bumblebee knocks one of the cars, flipping it over, but another drives up alongside Optimus. One of the masked goons climbs onto Optimus and starts attempting to sever the trailer. After Prime knocks the car off the mountainside road, Fowler climbs out and grabs the masked goon, but loses him before he can start an interrogation.

The fellow in the helicopter makes contact over a walkie talkie and introduces himself as Silas, part of the MECH organization, which intends to steal the DNGS for their own use. One of the cars pulls up behind Optimus and the MECH goons blow the trailer's back door open, only for Arcee to jump out in motorcycle mode and flip their car, causing it to explode. While Optimus warns Fowler not to take Silas lightly (due to personal experience), Ratchet informs them that they're nearing the rendezvous point.

On the Nemesis, Soundwave has intercepted the communications, and Starscream sends a bunch of Vehicons to join the party.

The Autobots reach the rendezvous point and duck into a rail tunnel alongside a train. Bulkhead seals off the incoming end. A short time later, they and the train emerge from the other end of the tunnel, and Silas continues to follow the Autobots. As luck would have it, the Vehicons take this opportunity to appear and open fire on the convoy. The Autobots avoid getting hit, but Prime's trailer is shaken loose and explodes. The Vehicons transform and move in, forcing Optimus to inform Fowler that they're going to have to break cover to survive. Silas observes the fight and notes that the rumors he's heard of living technology are true. He lets Fowler know that he's aware that the DNGS was transferred onto the train while the Autobots were in the tunnel, and the helicopter moves off to intercept the cargo. Unfortunately, while Fowler's giving Optimus the bad news, the Autobot leader takes a tree trunk to the face and falls off a nearby cliff.

The kids have a frantic discussion about a Plan B. Miko's in favor of Ratchet Ground-Bridging the kids onto the train so they can fight the MECH goons. Ratchet is unsure about the safety of such a plan until Raf explains how he can assist using his computer skills. With Raf's help, Jack and Miko are soon on the train. As the MECH helicopter tries to land on top of the train, Raf uses his computer to flip a point switch, making the train go off along another line. In response, the helicopter's pilot hacks Raf's laptop, causing it to short out. On the second try, the helicopter lands atop the carriage the DNGS is in, and the MECH guys start cutting through the carriage roof.

Not far away, the Autobots continue their fight with the Vehicons. Optimus comes around and sees the train in trouble.

Miko and Jack grab weapons, which they wave at the MECH guys when the ceiling's opened. Back in the chopper, Silas spots Optimus running alongside and sounds a retreat. As the helicopter heads away, he fires a missile and takes out the track ahead of the train. Due to Raf's laptop being out of commission, Ratchet no longer has the train's coordinates and can't Bridge the kids out. They prepare to jump, but Optimus zooms past, grabs the front of the train and brings it to a halt in the nick of time. Hovering in the helicopter nearby, Silas promises that next time the playing field will be leveled. Optimus reports back to Ratchet that the kids and the DNGS are safe, but notes that a new player has entered the game...

Tropes:

 * Big Damn Heroes: Optimus shows up just in time to stop the train that was carrying Jack, Miko and the DNGS from going off the rails.
 * Car Fu
 * Fun With Acronyms: The DNGS, pronounced Dingus
 * In Harms Way: Jack and Miko are two kids intercepting heavily armed goons. Really?
 * Mugging the Monster: When trying to steal the DNGS, MECH thinks they are only dealing with "an unarmed civilian truck". The Autobots don't even need to transform to trash the MECH cars.
 * No MacGuffin No Winner: Silas tries this, but Optimus manages to save the DNGS.
 * Ship Tease: One scene implies that Jack may have some feelings for Miko. Seems pretty one-sided, though.
 * Trainstopping: Optimus does this. For bonus points, he stops it slowly enough to avert Inertia Is a Cruel Mistress.