In Citadel S01E03, Infinite Shadows, Bernard (Stanley Tucci) is tortured by Dahlia (Lesley Manville) for information. Meanwhile, Nadia (Priyanka Chopra Jonas) and Mason (Richard Madden) seek a safe house in Spain. Flashbacks reveal their past connection as they work together to save a fellow agent, Carter Spence (Osy Ikhile).
Nadia disables the tracker on the Citadel X Case to avoid being followed by Davik (Roland Møller). As she tends to Mason’s wound, their conversation reveals their past relationship, which they both recall differently. A decade ago, Nadia saved Mason on a dangerous mission in Iran, and they grew close afterward. In the present, Nadia receives a coded message about a package waiting for her.
Dahlia threatens Bernard’s family, as well as Mason’s, to force him to reveal a password for a Citadel AI that tracks Uranium. Abby (Ashleigh Cummings) shares her own memories with Joe (Moira Kelly), Bernard’s ex-wife, about meeting Mason. Dahlia continues her torture of Bernard, but he turns the tables by revealing a truth about Anders’ loved one, Brielle.
Mason talks to Abby about Nadia, and Nadia later convinces Mason to focus on protecting his family. However, he insists on helping her save Carter Spence, who is being held by crime boss Balduino Basto. Posing as his old self, Mason infiltrates Balduino’s organization, with Nadia guiding him from a distance.
Nadia hacks Balduino’s phone, but the crime boss hints that she was the one who sold out Citadel. Mason escapes by taking Balduino’s son hostage. In the car, he confronts Nadia about her past with Mason and whether she was the mole. Nadia insists that she wouldn’t be helping if she was the mole.
As the episode ends, Bernard uses a photo of Mason’s family to convince Anders (Roland Møller) that everything he knows is a lie, and that Abby is actually Brielle.