“I thought you already did.”— Mark (to Serena Joy) when she refuses to betray her country.
Mark Tuello is a recurring character in seasons 2 and 3 of The Handmaid's Tale. He is a representative of the US Government-in-Exile.
In the TV Series
Season Two
Smart Power
Mark meets Serena Joy in the Canadian hotel that the Waterfords are staying at during their visit. Initially, Serena assumes that he works with the press. He reveals to her that he is a representative of the US Government-In-Exile. He attempts to persuade Serena to start a new life away from Gilead, offering safe passage to Honolulu and encouraging her to write a book about the Republic that they will publish.
Realizing that he seeks to use her a propaganda tool, Mark appeals to her desire to have a baby, arguing that American scientists have been working on the fertility crisis for years and have the ability to make her fertile again. She would also be guaranteed 'freedom' (presumably not facing legal action for her involvement in the coup d'etat).
Serena states that she will never betray her country, to which Mark says that she already did (in betraying the United States of America and being part of a coup d'état which overthrew the legitimate American government).
Season Three
Unknown Caller
Mark meets Serena at the Toronto airport for her meeting with Luke and Nichole. He takes her to the terminal, telling her there is a change of clothes waiting in order for her to "blend in" as the meeting is going to take place in a public area. He then introduces Serena to Luke, and is present for the whole meeting from the sidelines.
After the meeting is over, he takes Serena back to the changing room and brings up the "treason and coconuts" offer he made to her the last time they met, Serena still refuses. He leaves her alone to change back into her standard Wife outfit. It has been suggested that the phone Serena finds in her purse with a note reading "If you need me" was put there by Mark.
Witness
When Serena returns to Gilead after having seen Nichole once more, she becomes increasingly desperate to see her again. After several months of failed negotiations, in an effort to facilitate another reunion with Nichole, Serena convinces Fred to meet with Mark near the Canadian border under the pretense that he would be able to help return their daughter to Gilead.
Liars
Mark meets Serena and Fred on the Gileadean side of the border and asks them to follow his car into a safe place where they will be able to talk just "up ahead." After reaffirming that Mark is trustworthy, Serena ultimately convinces Fred to follow his vehicle, though he becomes increasingly suspicious when he realizes that the journey is much longer than expected. Unbeknownst to Fred, Mark had lured him and his wife into Canada.
Citing war crimes and documented international human rights violations, Mark carries out an arrest with the help of the Canadian military. Fred and Serena are both detained as Mark watches.
Sacrifice
Mark comes to Serena's prison cell to prepare for her visitation with Nichole, only saying that she has been detained. When Moira arrives with the baby, he introduces Serena to her as well as a social worker, and lays down the ground rules for the visit - Moira is to stay in the waiting room while the visitation is taking place. He hears Moira's entire diatribe against what Serena and Fred have done to her and June and takes her out of the room. Later, in Fred's cell, Fred blames him for Serena's exploitation of Nichole for her own gains. Mark replies that Serena's too smart to be manipulated and tells Fred that it should be considered an opportunity to understand Gilead a little better, He also says Luke has requested a meeting, to which Fred gives his consent. Mark introduces Luke to Fred, and leaves to let the two men talk.
The next day, Mark visits Serena with a box of pizza, telling her that Toronto makes it good. When Serena implies that things like that are contraband, he simply tells her to "eat up the evidence". He also gives her a magazine and some newspapers to read, highlighting an article about media bias in relation to religion.