Who Is Donovan’s Inside Source in Slow Horses?

Slow Horses,’ Apple TV+’s spy thriller show, revolves around a group of MI5 Agents assigned to the Agency’s least compelling department, led by the perpetually grouchy but genius Agent Jackson Lamb. Each season follows the agents as they face new threats while their colleagues continue to undermine their worth. In the show’s third season, a new mystery arises revolving around the Agency’s inner secrets as an ex-agent, Sean Donovan, attempts to uncover them as a part of his revenge plot.

After Donovan’s partner, Alison Dunn, dies at the hands of the MI5, who suspects her to be a traitor seeking to leak a classified Agency File, the former decides to see Alison’s mission to the end. Through a complicated trap involving several double-crosses, Donovan and his accomplices reach closer and closer to their goal. Yet, the group’s convenient access to sensitive information suggests Donovan’s connection to an inside source within the MI5, compelling viewers to wonder about the mole’s identity. SPOILERS AHEAD!

The Mastermind Behind Donovan’s Plan

Donovan’s contentious relationship with the MI5 Agency becomes known early on in the season, which begins with the story of Alison Dunn’s assassination. Even though Donovan had agreed to investigate Alison at his superior’s commands, his feelings for the woman were genuine. Therefore, after she died, and the Agency covered up her death as a suicide, it left her partner devastated.

As a result, Donovan decided to seek out the catalyst behind Alison’s death, The Footprint File, and leak it to the public as Alison had wanted. Nevertheless, the file was a well-kept secret at the Agency, guarded by the Director-general, Ingrid Tearney herself. Since the information could directly incriminate Ingrid and lay waste to the woman’s career, she ensured to keep the files away from attention, constantly rotating them from facility to facility.

Therefore, Donovan’s mission to bring the Footprint File into the light was a direct threat to Ingrid. Yet, he wasn’t the only one targeting the MI5 Head. Diana Taverner, the head of MI5 Second Desk, has been trying to become the Agency Head for a long time. Nevertheless, after Ingrid’s promotion, the other woman realized the chances of it happening were slim. Given her age and Ingrid’s refusal to retire early, Diana knew that by the time her turn arrived, the Agency would prefer to hire someone else.

As such, Diana needed to find a way to snatch away Ingrid’s job. Thus, the discovery of The Footprint File gave her the exact opportunity she had been looking for. The files detail Ingrid’s involvement in a secret device tech run that ended in numerous deaths. For the same reason, Diana realizes that if she manages to leak the file, it will ruin Ingrid’s career and get her fired from the Agency. Nevertheless, she can’t do the job herself without bidding her own career goodbye.

Consequently, Diana seeks out Alison Dunn’s former partner, Sean Donovan. She knows the man has an adequate motive to want revenge against the Agency in the exact way she needs him. As a result, after anonymously approaching him on the Internet. After convincing him of her high-level position at the Agency, Diana shared details about the Footprint File with him. By then, the woman had been assigned authority over a filing facility, meant to be a punishment for her previous missteps.

Nonetheless, Diana ends up using the facility to her advantage and ensures the Footprint File remains inside the building. Afterward, through subtle manipulation, Diana ensures The Home Secretary hires the Cheiftans for his Tiger Team operation at the Park. Likewise, the Chieftans get influenced to hire Donovan and his team. As such, Diana orchestrated the entire operation without ever leaving a tangible trace. In the end, Diana’s plans unfold as planned, albeit with a few blunders, and the woman achieves her ambitions of becoming the MI5 Head.

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