Sean Kent Davis, codename Ewan Macleod, is Nancy's Cathedral contact.
In 2013, when Nancy is called to investigate her mother's death in Scotland, she is told when she arrives that Cathedral had not in fact summoned her, and that she had been lured to Glasgow under false pretenses. Nevertheless, a Cathedral member called Ewan had been set up as her contact to keep her safe. Ewan is not his real name, but his codename.
After Alec stages an attack in Nancy's room, the elevator sends her down to Ewan's headquarters, where she finds him tied down to his chair.
After Nancy and Zoe are gassed in the elevator and thrown into the trash compactor, Zoe decides they should tap Ewan's computer again. Nancy does so and finds that he is working for Revenant. She finds his lair underneath the train station and sees a series of messages he received from Revenant, indicating that he contacted them out of interest -because he felt like a small, inconsequential man and wanted to feel important- but they soon turned on him when he was no longer helpful and said that he would be captured or killed. The messages say that Revenant knows his real name is Sean Kent Davis.
Ewan had probably tied himself up to make it look like Revenant was after him and had stolen the formula from Nancy and Zoe. When Nancy confronts him, he had already made four bombs, but Nancy, with Zoe's help, disarms them. Ewan is then arrested.