Star Wars Rebels gives us a filler episode in Warhead, but not an unentertaining one. Zeb (Steve Blum) takes center stage with Chopper and AP-5 (Stephen Stanton) as sidekicks. I love AP-5's smug demeanor. He's a rare comedic element in the series. We also get another appearance by Agent Kallus (David Oyelowo) as the rebel's secret informer, Fulcrum.
Warhead opens with Star Destroyers launching dozens of probe ships into space. One of them crash lands on Atollon. An Imperial Infiltrator Droid, EXD-9 (David Acord), emerges. It takes a few steps before being attacked by the freaky Krykna spiders. The droid is an homage to Ralph McQuarrie's original concept art of C3PO.
Back at the rebel base, Hera (Vanessa Marshall) chides Wedge and Hobby to get to their ships. She's leaving Zeb in charge while the rest of Phoenix Squadron goes for combat exercises. Zeb is not happy to be stuck with Chopper and AP-5, who's only concern is to inventory their supplies. AP-5, in fantastic dry droll, is stunned as well by Zeb's leadership assignment.
Zeb sulks for a bit before a soldier informs him of a meteor strike nearby. He takes Chopper to investigate. They find the dead Krykna on top of the deactivated droid. It looks harmless, so Zeb decides to take it back to the base. Chopper strongly disagrees and wants to destroy it. Meanwhile back at the Star Destroyers, a soldier informs Agent Kallus that they've lost contact with one of the Infiltrator Droids. He's about to send a search team when Kallus stops him.
At the base, AP-5 is doing inventory and lamenting the lack of organization by the rebels. Zeb brings the EXD-9 and asks AP-5 to power it on. The EXD-9 hums to life, and then quickly begins cataloging everything it scans. It brands Chopper as obsolete. AP-5 is delighted to have someone assist him. Zeb laughs as he's told of an incoming message from Fulcrum.
Fulcrum aka Agent Kallus, the rebel's most important spy, tells them of the Infiltrator. He also explains that the droid will be searched for if not heard from soon. Zeb is aghast as Fulcrum sends a diagram of the harmless-looking droid, which transforms into a terrifying weapon. He races back to AP-5. Suddenly, the EXD-9 overhears them discussing the rebel base. It transforms into battle mode and attacks them.
Zeb manages to blast its arm off. The EXD-9 runs away, dripping fluid. They chase it down and come upon a hapless R2 unit with its power cell torn out. The EXD-9 is repairing itself. Zeb tells Chopper to attract its attention as bait. Then he'll hold it down while AP-5 deactivates it. AP-5 has zero faith in the plan, but follows them anyway.
The EXD-9 sees Chopper and gives chase. Zeb jumps down from a catwalk. He holds it down as AP-5 struggles to turn of its power. They succeed, but notice that the droid has begun to countdown like a bomb. AP-5 realizes it has a proton warhead in its chest. They are about to be blown up when Chopper freezes the timer. Zeb has an idea. They need to have to the droid report back to the Empire, but they can send it with a gift.
AP-5 reprograms the droid out of battle mode. Then gives it an order to return. They follow it as it gets back to the ship. It's about to send out a signal when Zeb blasts the communications dish. The EXD-9 closes the door then dutifully takes off into space. The pod finds its Star Destroyer and lands. Stormtroopers open the pod door to find the droid counting down. Agent Kallus is on the bridge of his ship as the adjacent ship explodes from the warhead.
On Atollon, AP-5 commends Zeb on his plan. Hera and Phoenix Squadron return from their exercise. They are shocked when Fulcrum calls in to congratulate Zeb on the maneuver. As the rebels cheer another victory, the scene cuts to Grand Admiral Thrawn (Lars Mikkelsen) looking at a hologram of numerous systems.
Thrawn asks Kallus what he thought of the warhead incident. Kallus responds it was a brilliant move. Thrawn agrees, but then states that it confirms the rebel base was indeed on a planet that an Infiltrator was sent to. The hologram resets to only a few remaining planets. Thrawn has significantly whittled down the possibilities of the rebels location. The Empire tightens the noose as Star Wars Rebels continues on Disney XD.