The Republic advance on the massive Geonosis foundry continues. Anakin and Ahsoka brief their troops on an approach that will require their forces to cross a bridge spanning an immense canyon. It will be a difficult assault, as the bridge forms a natural bottleneck that concentrates the clones into an easily targeted cluster.

Luminara Unduli and her Padawan, Barriss Offee, arrive by gunship along with their clone forces and meet with Skywalker and Tano. Luminara provides an alternative to Anakin's forceful frontal assault on the droid factory -- infiltrating the catacombs below the factory and taking out the foundry's reactor with explosives. Barriss comes prepared -- she has already memorized all 200 junctions of the underground maze.

Luminara suggests that she and Skywalker use the clone army to distract the Geonosians while the Padawans carry out the sabotage mission. Anakin is hesitant, for he worries that Ahsoka is not prepared to undertake an unsupervised assignment such as this. He relents at Ahsoka's insistence, and Luminara equips the apprentices with synchronized chronometers to keep track of them.

Inside the foundry, Poggle the Lesser and the tactical droid TX-21 monitor the factory's efficiency. It is operating at 50 percent capacity, but it has already churned out ten garrisons of new troops ready to deploy. Their new weapon, super tanks capable of repelling Republic artillery, approaches operational status as well.

The Republic forces march toward the bridge and are immediately swarmed by battle droids and Geonosians. As the armies tangle on the surface, Barriss and Ahsoka climb down to the dry riverbed of the canyon. Barriss cuts a passageway into the catacombs, and leads the way into the darkness.

Ahsoka and Barriss creep through the darkened catacombs, trying to avoid Geonosians sentries. They stumble into a den of sleeping Geonosians, slinking past the snoozing drones. A dead end gives Barriss momentary doubt, but she soon recalls the correct direction.

On the surface, clone AT-TE tanks provide heavy firepower to cut through droideka squads. At TX-21's prompting, Poggle the Lesser allows 20 of the experimental super tanks to roll into combat. Anakin orders Rex to fire on the new targets, but the clone artillery has no effect on the ray-shielded armor. The super tanks return fire, wiping out the Republic artillery line.

Inside the power plant, Ahsoka and Barriss have made their way to the foundry reactor, but their approach has been spotted by a Geonosian spy. The spy has informed Poggle, who orders TX-21 to dispose of the intruders.

The tactical droid deploys winged Geonosian warriors as well as a super tank into the reactor room. The Geonosians dispose of the few explosives that the Padwawans have set. Ahsoka destroys TX-21 with an explosive she attaches to the tank next to him.

The super tank bombardment tears through the Republic armor, causing the AT-TEs to collapse under the withering assault. Luminara and Anakin order their troops to fall back, drawing the tanks onto the bridge.

Meanwhile, in the reactor core, Ahsoka is lifted into the air and dropped by a flying Geonosian. She hits the reactor station hard, and is knocked unconscious. Having removed all the explosives, the Geonosians scatter into access hatches. Barriss is left alone to face the super tank by herself.

On the surface, the super tanks rumble over the stone bridge as Anakin and Luminara acrobatically climb to the bridge's underbelly. They swing hand-over-hand over the precarious height, affixing thermal detonator explosives at key points. Emerging on the opposite end behind the tanks, Anakin triggers the remote detonator, sending the tanks into the canyon with the exploding bridge.

Anakin's triumph is soon clouded by his concern for the Padawans. According to his chronometer, the reactor bombs should go off at any moment, and yet there is no sign of the apprentices. The heavy gates to the foundry open and a fresh wave of battle droids emerge.

In the reactor room, Barriss leaps atop the super tank and cuts her way into the armored vehicle, slicing through the droid pilots. Ahsoka awakens and joins Barriss in the tank, but without the explosives to blow up the core, she'll have to improvise. Ahsoka will destroy the core with the tank, sacrificing herself and Barriss in the process.

She sends a quick communication to Anakin to inform him of their plan, then trains the tank cannons on the reactor. Anakin and Luminara watch in shock as the entire foundry collapses in a chain of explosions with their apprentices caught inside.

An immense dust cloud envelops the blast site. Anakin tries to contact Ahsoka via his comlink. He is determined to find his apprentice, but Luminara is much more accepting of their fates. Skywalker orders the tank lifters to clear the debris.

Under tons of rubble, in the darkened control cabin of their trapped tank, Ahsoka and Barriss illuminate the darkness with the twin glows of their lightsabers. Ahsoka uses one of the tank's smaller power cells to boost the signal on her wrist comlink.

As the lifters peel off layers of wreckage from the crater, Anakin suddenly gets a pulse on his comlink from Ahsoka. Redirecting the clean-up efforts, Anakin and Luminara use the Force to lift the debris. Sunlight streams into the shattered tank hull and Ahsoka and Barriss realize they're saved. They emerge, shaken and coughing, and are reunited with their mentors.