|“||But...I'm really grateful for what you did back then...! If you hadn't given me so much courage, I...I might have died on that train...||”|
Mary Beriam (メリー・ベリアム, Merī Beriamu) is the daughter of Senator Manfred Beriam and Natalie Beriam. During the hijacking of the transcontinental express Flying Pussyfoot en route to New York City in December 1931, she and her mother are taken hostage by the Lemures.
Aboard the Flying Pussyfoot, Mary ties her brown hair back with a bow and wears a pink shawl over a pink dress with a pearl necklace, over which she wears a burgundy coat when in the train station.
In 1931, Mary is a young, innocent girl prone to shyness, easily intimidated by strangers. She retains this timidity in her early teens; however, she appears to have some higher degree of perceptiveness than her younger self. She is kind and appreciative, and has no compunctions about sharing her emotions with those around her.
On the evening of December 30, 1931, Mary and her mother board the Flying Pussyfoot in Chicago's Union Station for New York City, where they plan to visit Senator Beriam. The two share a First Class cabin with Czeslaw Meyer, and after some hours pass decide to have dinner in the dining car. There, Czes accidentally bumps into Jacuzzi Splot, who is sitting on one of the bar stools.
Though shy at first, intimidated by Jacuzzi's tattoo and Nice Holystone's scars, Mary introduces herself at her mother's request. She is among those who listen to and are frightened by Isaac Dian's tale of the Rail Tracer, a monster who preys upon trains; Jacuzzi is so frightened that he bolts for the conductors' cabin when Isaac cannot remember how to prevent the Rail Tracer from coming.
Not long after, three Lemures, Vicky the White Suit, and Nick simultaneously converge upon the dining car and make demands of the passengers. Isaac and Miria Harvent make sure Czes and Mary get down before doing the same, while Vicky shoots and wounds one of the Lemures before being shot dead. When White Suit Ladd Russo enters the room, he shoots dead one Lemur, lets the wounded Lemur escape, and boxes the remaining Lemur to death.
Following Turner's ejection from the dining car, Natalie tells Mary to go find a place to hide with Czes and stay hidden until morning. Czes leads Mary to a broom closet in the Second Class washroom and instructs her to remain put while he checks out the other cars. Alone and in pitch-dark, all Mary can do is crouch down and cry in fear at the machine-gun fire in the distance.
A droopy-eyed White Suit later discovers Mary in the closet and covers her mouth, but Chané Laforet stabs him in the back before he can do harm. Mistaking Chané for the Rail Tracer, Mary screams to no avail. Chané or another Lemur ties her hands behind her back and escorts her to the frontmost cabin of First Class, where she is reunited with her mother and joins her in Lemur captivity under the watch of an armed Lemur. While hostage, Mary worries desperately for Czes' safety in the meantime.
Rescue eventually comes in the form of a stowaway called Rachel, who takes care of the guard before helping Natalie and Mary out of the window and onto the roof. On her advice, Natalie and Natalie run for the dining car whereupon they reunite with Isaac, Mary, and Czes. Mary embraces Czes, happy that he is safe.
Before entering New York City, the train stops so that its cars and engine may be switched out while the police carry out an investigation and accompanying arrests. The investigation takes two hours, after which the Flying Pussyfoot finally arrives at Pennsylvania Station two hours late at 2:00 PM, December 31. After reuniting with Manfred, Mary thanks Rachel and declares she wants to grow up to be a great person like Rachel is.
By February 1935, Mary has come to know Carzelio "Cazze" Runorata from the Runorata Family. She accompanies Cazze that month to the Martillo Family casino, where he plans on picking up Melvi Dormentaire—and where she unexpectedly finds Czes waiting outside the premises with Annie. She eagerly engages Czes in conversation, observing that she is taller than him and telling him how grateful she was back on the Flying Pussyfoot for his company; without the courage he gave her, she might have died. Mary then pulls Czeslaw into a hug. Standing behind her, Cazze asks if 'that boy' is the one who rescued her back on the train, and tells Mary to wait outside while he and his companions enter the casino to 'visit' Melvi and his hired-bodyguard Felix Walken.
Mary and Czeslaw's reunion is cut short when Melvi and Claire Stanfield emerge from the casino. Czes flees "at full speed," leaving a mystified Mary in his wake, and she suspects something is 'off' about the situation when she notices Annie has vanished as well. Carzelio, who has also reemerged, thanks Mary for waiting and tells her that he will accompany her home. He brushes off her thanks by explaining he has a letter his grandfather wants him to deliver to Mary's father.
Czeslaw Meyer: A friend whom Mary met aboard the Flying Pussyfoot, and unbeknownst to her, an immortal. The two played with each other while on the train, running about with abandon. Mary views Czeslaw fondly, and is extremely grateful to Czeslaw for giving her courage on the train. The impression he made on her was strong enough that she still remembers him years after the incident.
Carzelio Runorata: Mary is acquainted with Carzelio, probably through her father's connection to the Runoratas, and like all of his friends she calls him Cazze. The two traveled together to pick up Melvi and Felix, but he went in without her when she reunited with Czeslaw.
Natalie Beriam: Mary appears to have a close, loving relationship with her mother. Natalie is willing to risk her own life for her daughter, standing up to the hijackers in the dining car when they ask where Mary is, demonstrating the love she has for her daughter. Mary refers to her mother as 'mama'.
- It is possible that Mary was born in 1921; in 1931 The Grand Punk Railroad: Local' she is described as looking around the same age as Czeslaw, who was around ten years old when he drank the elixir.