Richese and Vernius
After Yueh first graduated from the Suk School in 10,112 AG, he married the Bene Gesserit sister Wanna Marcus. He first served as physician of House Richese, and then secretly dignosed Baron Vladimir Harkonnen's venereal disease given to him by Gaius Helen Mohiam. Later, after the disfigurement of Rhombur Vernius, brought on in the skyclipper accident over Caladan, Yueh entered the service of House Vernius. After the tragedy of 10,188 AG, when Tessia Vernius was rendered comatose on the planet Ix, and Rhombur was killed on Chusuk, Yueh entered the service of House Atreides household as the physician of Leto Atreides I.
Agent of the Harkonnens
The Baron had taken Yueh's wife Wanna prisoner, and threatened her with torture and death, unless Yueh complied with his demands. Harkonnen also distracted Leto's Mentat Thufir Hawat from discovering Yueh by guiding Hawat toward another suspect: Leto's Bene Gesserit concubine Lady Jessica Atreides. Jessica herself eliminated suspects though her Bene Gesserit skills of observation and Truthsaying, with Hawat noting that testing Yueh in this way would be an empty gesture since he's conditioned by the High College. Jessica was troubled, however, with the knowledge that Wanna was a Bene Gesserit slain by the Harkonnens, when she heard his hate when Yueh spoke about them.
The Atreides were soon attacked by Harkonnen forces (secretly supplemented by the seemingly unstoppable Imperial Sardaukar), and Yueh followed orders and disabled the protective shields around the Atreides palace on Arrakis. Yueh stabbed the Duke with a poison dart, and while he was paralysed, replaced one of the Duke's teeth with a false one that could expel poisonous gas. The idea was that the Duke would have an opportunity to kill the Baron, using the poisoned gas tooth. Unfortunately, the plan failed, and the Duke was killed.
The Death of Wellington Yueh
Yueh discovered that Wanna was indeed dead moments before De Vries killed him, and Leto's assassination attempt of the Baron only kills Leto and De Vries. Leto and Jessica's son Paul Atreides fled into the desert with Jessica, aided by survival kits left for them by Yueh. Both were presumed dead, but were alive and living among the planet's native Fremen.
Yueh died by the hand of de Vries, stabbed in the back by the twisted Mentat who had come to the logical conclusion that the traitor had outlived his usefulness. He died with the knowledge that his wife had in fact been dead for years, slain by the Harkonnens and kept a secret, so that he could do their bidding.
As a Ghola During Kralizec
Yueh on the Ithaca
Yueh was resurrected as a ghola on the no-ship Ithaca (over 5,000 years after his death) to aid in the coming final battle with mankind's Great Enemy. Renegade Bene Gesserit Sheeana's ghola program also includes new incarnations of Paul Atreides, Jessica, Chani, Stilgar, and Liet Kynes among others.
As the Ithaca wandered the cosmos over the next decade, the young Yueh ghola was wracked by feelings of intense guilt over the actions of the "original" Yueh, and fear that he would repeat those mistakes. Though he did not yet possess those memories, he read all of the histories, and reached out to the reborn Jessica ghola for forgiveness. Similarly, without memories but fully aware of their past, a kind Jessica assured Yueh that it only matters what he choses to do in this current life.
As a ghola's memories can only be restored by subjecting the ghola to an intense personal trauma; individually-tailored scenarios must be devised for each ghola. Realizing young Yueh's great fear of having his memories restored, Sheeana led Yueh to believe that she could restore his memories easily, and used her skill as a sexual imprinter to began the process. As Yueh's own intense resistance unlocked his past memories, he recalled how Piter De Vries and Baron Harkonnen had broken the Suk conditioning by repeatedly forcing him to watch Wanna be systematically tortured and humiliated, and as he awakened, Yueh cursed the Sisterhood.
Manipulated by the Rabbi
Later, on the ship, Yueh was manipulated by the Jewish Rabbi into believing that an unidentified new ghola being created is that of Piter De Vries. Horrified, a tormented Yueh poisoned and killed it, and the once-human axlotl tank in which it was gestating, knowing the consequences for his actions will be severe. Yueh admitted his crime, and expected understanding though not forgiveness. All were shocked, especially Jessica, when Sheeana announces that the ghola had not been De Vries, but Leto Atreides I.
A few months later, Yueh is thought to be the saboteur wreaking havoc on The Ithaca, but it was later revealed that a pair of Enhanced Face Dancers have murdered and replaced the fellow passengers of the Rabbi, and the ghola of Thufir Hawat. Yueh was relieved when he realizes that it was a false Rabbi who had deceived Yueh about the Leto ghola.
On the Day of Kralizec
After the Ithaca was captured, and brought to Synchrony, Yueh was brought to the Cathedral with rest of the Kwisatz Haderach group. Later, during the climactic knife fight between Sheeana's Paul Atreides ghola and a twisted Paul ghola named Paolo, Paul was mortally wounded, and Yueh worked frantically to save his life. He realizes that Paul was beyond medical assistance, and will surely die. But Paul's memories are restored by the trauma of impending death; as Jessica reminded him of his Bene Gesserit-trained physiological control. Paul managed to repair the worst of the damage internally using this training; though weak, he survived.
Meanwhile Yueh, secretly no longer bound by his Suk conditioning, was called over by the ghola of Vladimir Harkonnen to bring Paolo out of his prescient coma. Yueh broke the news to those assembled, including the Thinking Machine rulers, Omnius and Erasmus, that Paolo would never come back to reality, and will starve and thirst to death. After some taunting by Vladimir again, Yueh grabbed Paolo's knife and stabbed Harkonnen through the throat and up into the brain, killing him.
With Leto and Jessica on Dan
Eleven years later, Yueh lived on the original Atreides homeworld of Dan, and helped Lady Jessica restore it to its former glory. He had finally found peace, and both look forward to the adulthood of the new Leto I ghola in their midst, now ten years old.