Warning: the following contains SPOILERS for Severance.
Severance is focused on the mysterious activities of controversial mega-corporation Lumon Industries, and there's evidence to suggest that Irving is the one who's working with Petey to help severed employees get out. It's clear that resigning from Lumon Industries isn't so easy for those who've already agreed to get a severance chip implanted into their brains. Petey couldn't have gotten out without help from a spy or a mole who's working from the inside. As for who that someone is, there are plenty of reasons why Irving is the most likely suspect out of the entire cast of Severance.
Corporate espionage is a recurring element in the hypercapitalist dystopia of Severance. Petey, a formerly severed employee with reintegration sickness, relies on subtle spy tactics in order to contact Mark and enlist his help to get others out. Helly, the new recruit on the severed floor, employs similarly subtle tactics to try and send messages from the severed floor to her outie. Meanwhile, severed floor supervisor Harmony watches over Mark's outie as Mrs. Selvig, goes inside Mark's home when he's at work, and even steals his personal belongings. Although Mark's outie and innie are both loyal to Lumon Industries, Mark quickly agrees to harbor Petey, who just escaped from being severed.
Related: Severance: What Lumon's Numbers Mean — Every Theory
Severance makes it clear that in this corporate dystopian world, everyone is hiding something. As the process of severance splits the memories of employees between their working time and their life outside of the severed floor, it's much more difficult for anyone to steal Lumon's secrets, let alone help severed employees escape the company.
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