During the Republic invasion of Umbara, Fives and the young clone troopers Tup and Hardcase were attacked by a fearsome, shadowy predator known as a vixus. The quick-thinking ARC trooper saved himself by hurling a thermal detonator into the beast’s maw.

When Pong Krell took over command of the 501st Legion on Umbara, Fives was one of the Jedi General’s fiercest critics, decrying Krell’s insistence on full-frontal assaults that were guaranteed to cost many clones their lives.

Krell ordered the clones to make a suicidal frontal attack on an Umbaran airbase, leaving Fives on the edge of open rebellion. Captain Rex sent Fives and Hardcase to infiltrate the airbase. The clones succeeded and stole two Umbaran fighters, giving the clones the air support they desperately needed.

The clones took the airbase, but Krell ordered them to press on to the Umbaran capital. Fives proposed flying Umbaran fighters into orbit to attack a key Separatist supply ship, a plan Krell rejected as a frivolous adventure. When Fives decided to disobey the Jedi General’s orders, Rex warned his friend that he wouldn’t be able to cover for him.

Fives’ plan succeeded, but a furious Krell ordered him and clone trooper Jesse executed for insubordination. The other clones refused the order and Rex freed Fives and Jesse.

After Krell sent clone troops into battle against each other, Rex ordered his men to arrest the Jedi General for treason. Fives and Jesse joined the attack against this formidable opponent.

The clones captured Krell, but Rex’s training made it extremely difficult for him to contemplate executing a Jedi. It was the clone trooper Dogma – who’d been Krell’s most ardent supporter – who carried out the sentence, yanking Fives’ blaster from its holster in a fit of anger and shooting the traitorous Jedi.

On Ringo Vinda, Fives watched with concern as Tup became confused in battle. The ARC trooper urged his colleague to focus – but was stunned when Tup murdered Jedi General Tiplar, muttering that “good soldiers follow orders.”

Anakin Skywalker ordered Fives to figure out what had happened to Tup, but the Republic’s clone medics and medical droids were baffled – and Tup himself didn’t remember what he’d done. The clone was sent back to Kamino for study by the Kaminoan cloners who’d created the Grand Army of the Republic.

After Separatist droids ambushed Tup’s shuttle and kidnapped him, Fives joined a raid to retrieve the luckless clone. After the mission succeeded, Fives pleaded with Rex to let him accompany his friend to Kamino.

Shaak Ti and the Kaminoan scientist Nala Se examined Tup, but Fives became concerned that the Kaminoan didn’t truly care for the clone’s well-being. He convinced medical droid AZI-3 to take another look at Tup – and the droid found a tumor in the clone’s brain. AZI-3 surgically removed the tumor, but the procedure resulted in Tup’s death. A furious Nala Se ordered Fives arrested.

When Fives caught Nala Se switching Tup’s tumor with another sample, he knew something was badly wrong and escaped his guards, stealing the tumor and fleeing with AZI-3. Infiltrating the genetic records hall, the two discovered that Tup’s tumor matched nothing in Jango Fett’s genotype -- it was foreign tissue implanted for some mysterious reason.

Fives convinced AZI-3 to operate on him, and the droid found a tumor similar to the one in Tup’s brain – except Fives’ was healthy, while Tup’s had decomposed. Fives and AZI-3 discovered that the tumor was a bio-chip, and every clone had one implanted during his development. The furious ARC trooper confronted Nala Se, who said the chips were structural inhibitors designed to curb aggression – and had been implanted on orders from the Jedi Master Sifo-Dyas.

Shaak Ti, Nala Se and Fives traveled to Coruscant to present the ARC trooper’s discovery to Supreme Chancellor Palpatine in person. But on the way, Nala Se surreptitiously injected Fives with an unknown drug.

Fives and Palpatine spoke alone – but there was the sound of a scuffle and Shaak Ti entered the room to discover the clone standing over Palpatine with a weapon. Palpatine said the clone trooper had attacked him. A shocked Fives fled, escaping into Coruscant’s lawless lower levels.

Fives had stumbled upon not just a secret bio-chip but also a conspiracy that apparently included the Kaminoans and the Jedi and reached all the way to Palpatine himself. But he knew his story sounded crazy: Who would believe that Nala Se had drugged him and his assault on the Supreme Chancellor was staged? A desperate Fives asked his old comrade Kix to help him contact Captain Rex and Anakin Skywalker.

Rex and Anakin met Fives, who trapped them within a force shield so he could explain what had happened. But the ARC trooper knew he had no proof of what sounded like an insane, paranoid story. As Fives pleaded with his old friends, shocktroopers led by Commander Fox burst in and ordered him to surrender. Fives panicked and grabbed one of Rex’s pistols, but was shot and mortally wounded. Dying, he told Rex the conspiracy was bigger than anyone could have imagined.