Maria Ross

Second Lieutenant Maria Ross is an Amestrian soldier stationed in Central City under the command of Major Alex Louis Armstrong. Described as honest, decent and caring by her superior officer, 2nd Lt. Ross is an exemplary soldier capable of balancing her dutiful professionalism with her personable human side.

Ross first appears when she and her partner, Sergeant Denny Brosh, are assigned to escort and guard Edward and Alphonse Elric in place of Major Armstrong after the three alchemists arrive in Central. Ross and Brosh, just as many others, initially mistake Al for the famous "Fullmetal Alchemist" and find themselves confused as to the brothers' idiosyncrasies, but come to an understanding with them relatively soon. When the Elrics head toward their initial goal of the National Central Library's First Branch, Lt. Ross is given the unhappy task of informing them that the building and all the precious research materials inside had been destroyed the day before their arrival in a fire whose origin appears to have been arson.

Lt. Ross and her partner continue to guard the young alchemists as they find other means of acquiring and deciphering the information they seek, and are further shocked by the Elrics' casual rapport with such high-ranking officers as Lt. Colonel Maes Hughes as well as the exorbitant amounts of money they are able to throw around as part of their yearly government research grant. But the real shock comes when Ross and Brosh learn from the horrified Elrics that their code-breaking is complete and that the fruit of their labors has revealed that the Philosopher's Stone is made up of live human beings.

Manga
The two bodyguards are ordered by the higher-ranked Edward Elric not to mention this finding to anyone, but are soon forced to divulge the truth when Major Armstrong presses them.

Together, the Elrics, Armstrong, Ross and Brosh investigate deeper into the matter and deduce that the Fifth National Central Laboratory was involved with the gruesome manufacture of Philosopher's Stones. Despite Major Armstrong's order to stay away from the facility until proof has been found, Ed and Al sneak away in the middle of the night to investigate on their own, putting Ross and Brosh - as their bodyguards - in a bit of a spot. Ross, furious, heads off toward Lab 5 with her partner in tow.

They arrive on the scene in time to rescue Alphonse from Lab 5's armored guard, Barry the Chopper, Ross and Brosh each firing a round into the Chopper's right hand, disarming him. As they begin to question the murderous guard, an explosion within the laboratory triggers the compound's collapse. During the confusion, Barry flees the scene and Alphonse makes a move to enter the falling facility to rescue his brother, against Ross's protests. Fortunately, the Homunculus Envy exits the rubble with the wounded and unconscious Edward in tow, advising Ross to take care of him better. As Ross, misunderstanding the Homunculus' identity and role in Ed's injury, tells Envy to flee, the mysterious man disappears.

Considering the political complexity of the situation, Ross takes Edward to heal up in a clinic run by a friend of hers instead of taking him to a military hospital. When the Fullmetal Alchemist comes to and becomes upset that his research has to be interrupted by something as annoying as a hospital stay, Ross slaps the young Major and berates him for disobeying Armstrong's orders and sneaking away on his own and then apologizes formally, asking whether she will be reprimanded for raising a hand against a superior officer. Edward says that he had it coming and gives Ross permission to address him informally, putting her mind at great ease. A short while later, both Major Armstrong and Lt. Colonel Hughes come to visit Edward in the hospital and discuss the sum of the information they've collected regarding Lab 5 and the Philosopher's Stone. 2nd Lt. Ross, having had enough trouble on account of the accursed thing, stands outside the room with Sergeant Brosh and plugs her ears so as not to become further involved. However, they both suffer another major shock when Führer King Bradley himself stops by to visit Edward in the hospital.

When Edward's wounds heal and his is discharged from the hospital, the Elric Brothers head off to the town of Dublith in the Southern region and their bodyguards are finally dismissed from their duty. However, Maria Ross's problems do not stop there. Soon afterward, Lieutenant Colonel Maes Hughes is accosted and killed by Envy, disguised as Lt. Ross. Though Hughes is able to recognize the shape-shifting Homunculus as an impostor due to the accidental lack of a characteristic mole under Maria's left eye, he is shot point-blank and is found dead the next morning.

Some time later, caught in between the Homunculi's plans to placate Colonel Roy Mustang - who had been secretly and fervently investigating Maes Hughes' death since his transfer to Central City - and Colonel Mustang's plan to lure out the "Members of the Ouroboros", Maria Ross is identified as a suspect in Hughes' murder, publicly arrested and interrogated by Colonel Henry Douglas of Military Police Headquarters. While jailed, it is made clear that Ross' suspicion is based on on the fact that Hughes (posthumously promoted to Brigadier General) was killed by the same type and caliber of bullet used by the official military use handgun carried by the 2nd Lt. and that her gun had recently discharged one bullet - to protect Alphonse from Barry the Chopper at Laboratory 5. However, nothing about that incident exists on military records; it had been covered up. Additionally, a witness alleges to having seen Lt. Ross near the crime scene that night despite Maria's contention that she had been visiting her parents. However, the testimony of family members and close relations is not admissible as an alibi in military cases, so there is no way for Ross to defend herself against the charges. Sergeant Brosh, who also fired a round during the incident at Lab 5 is being forcibly kept away from the building where Ross' interrogation is being held, unable to testify on her behalf.

2003 anime
In the 2003 anime, 2nd Lt. Ross takes a slightly different role. After overhearing the truth of the Philosopher's Stone's creation, she deduces on her own that the depressed Elric brothers need alone time and diverts Major Armstrong from disturbing them. She goes in to check on the boys and sees that Edward appears to have given up on his search for the Stone and berates him for abandoning his dream when its goal is so much bigger than just him and his brother. Ross tells Ed that it is all right to be afraid and have to start over from a pile of wasted effort, giving him the strength to keep going. When Ed, Al, Ross and Brosh discover that Lab 5 may be the place where the Philosopher's Stone was being researched in secret, the 2nd Lt. demands that Fullmetal and his brother stay put for their safety and entrust investigating the facility to them. Edward complies, seeing Maria's determination, and she happily goes off to request permission from Armstrong to begin looking into the matter. Unfortunately, while doing so, Ross and Brosh hear the sounds of Scar attacking the library and rush back to protect Edward. They find Scar in the room where the boys have been studying and drive the serial killer out a window with gunfire. Looking around for signs of Ed and Al, they see that the boys were fortunately not in the room when Scar arrived. Unfortunately, signs point to the Elrics having snuck out of their room to head off to Lab 5 by themselves. Ross and Brosh inform Major Armstrong and Lt. Colonel Hughes immediately and they form a party to rescue the boys from the facility, where trouble will doubtlessly find them, and run into the Führer, King Bradley himself, who joins their party with a cadre of his own soldiers.

The rescue force arrives at Laboratory 5 and Ross acts as part of the team that enters the facility to find the brothers. When they finally encounter the Elrics in the lower reaches of the lab, they are shocked to find Edward's body going berserk, forced into triggering powerful transmutations from accidental contact with a large amount of Red Water. As the other soldiers watch helplessly while alchemical energy and wildly fluctuating automail make the Fullmetal Alchemist a hazard even to approach, Ross braves the storm of lightning and steel to embrace Edward tightly in her arms. The half-conscious boy mistakenly perceives Maria as his mother and calms down, halting all transmutations and allowing the soldiers to escape the facility as it crumbles to the ground.

Ross appears later in the series when Winry and Sheska investigate the Hughes' death on their own, recognizing Winry despite her disguise and inadvertently rescuing the two girls from Sloth. After Winry and Sheska hide out on Resembool, Ross and Brosh pay them a visit disguised as civilians. There, they encounter Hohenheim and Ross becomes almost instantly smitten with him.

At the end of the series, Ross is shown to continue working with the military, presumably in the same post as before.

Trivia

 * Maria Ross' prison processing number was W6186.