Stark is known as a legend in the biohacking community for his revolutionary ideas and results with terminally ill diseases. In 2009, Stark injected himself with a Malaria vaccine he created himself while on a live steam to prove that it worked after the FDA refused to authorize human trials without a ton of red tape. Stark then let a mosquito bite him, hoping the vaccine would prevent him from getting sick. Unfortunately, the vaccine didn't work and as a result of him taking it, half of Stark's face was completely paralyzed due to a hyperimmune response damaging his motor cortex. After that, Stark began researching ways to reverse his condition and those with a similar condition called MCDD. Around 2016, Stark recruited Dr. Ethan Webb to help him with his research after he was fired from Crown Life Pharmaceuticals.
In 2017, Stark acquired some advanced gene editing equipment through one of Reddington's companies and Reddington sought treatment from Stark for an unknown reason. Stark later used his job as a pharmacist at Greene to access patient files to find people with MCDD to run tests on a new treatment to cure it. Stark tested the treatment of Warren Kirby first and when it was successful, had Kirby help him set up a base of operations in one of Kirby's warehouses and medical equipment from a company Kirby is invested in: NexHack.
Stark begins his first set of human clinical trials with five patients with end-stage MCDD and instructs them all to inject themselves with the cure as it is illegal for them to do so. They all comply, but something goes wrong and all of Stark's patients die after injecting themselves forcing Stark and Webb to flee the warehouse before the police arrive. Start continues to seek out new patients for another MCDD trial, despite the protests of Webb. Stark manages to gather another set of patients ready for another batch of testing and gives the same instructions as before. The police barge in as one of his patients injects himself and Webb flees while Stark remains and witnesses in horror as the patient dies like the other patients.
Stark is then informed by Samar Navabi that Dr. Webb sabotaged the treatments with a nerve agent called Cylovex. Donald Ressler later tells him that Webb confessed his firing from Crown Life was faked so he could infiltrate Stark's research, sabotage it and steal it. Crown Life wanted to make sure it never reached the open market so they could continue making money selling drugs multiple times rather than a one-time cure. Stark laments on how badly Webb betrayed him while all the conspirators at Crown Life are arrested. Dembe visits Stark in holding and Stark reassures Dembe that his current predicament won't affect his research into Reddington's condition and will continue working.
Stark calls Dembe to tell him that he is in the blind testing phase of his clinical trials and will have results soon.
Reddington called Stark to treat Norman Devane after Ressler infected him with a engineered bacteria he created while Reddington interrogated him. Stark prescribes antibiotics to treat it until Devane states the strain he was infected with is antibiotic-resistant strain he created. Stark realizes who he is and Ressler, who was handcuffed to Devane, recognizes Stark. Devane reveals he started infecting children with diseases he created to test out his experimental treatments in preparation to use on him.
Stark admonishes him for experimenting on children, citing while he gave terminally ill hope, Devane infected healthy children. After Reddington gets the answers he needs he kills Devane, shocking Stark. Reddington assures him the Twins will clean the mess, protecting his lab and that Ressler will keep quiet about the whole thing. When Reddington asks about his own clinical trial, Stark regretfully tells him the treatment was ineffective.