Mary is a C&O class M1 who hates diesels and is willing to do anything to get rid of them.
Following World War 2, diesels began to gain prevalence on U.S. railways, putting the future of steam engines into uncertainty. The Chesapeake and Ohio railroad, being a major coal-hauling railroad, resisted the rise of diesels and paired up with Baldwin Locomotive works and Westinghouse. The result were 3 M1 steam turbines, Margaret (number 500), Mary (number 501) and Maya (number 502).
The M1s shared a lot in common with their diesel competitors, the only difference being the fuel type. All of the M1s were coal fired. The coal was stored ahead of the cab in a bunker, which could hold 26.5 tons of coal. The boiler was behind the cab with the turbine at the very rear. Their tenders carried 25,000 gallons of water.
The power, of course, came from the boiler, which operated at 310 psi. The steam then spun a turbine, which then powered 4 generators. The generators powered 8 traction motors on the 3 power bogies.
Each M1 had 5 bogies. The 1st and 3rd bogies, both of which were 4 wheel variants, were unpowered, the latter being support for the firebox. The 2nd and 4th bogies were 8 wheel power bogies. Only 3 of the axels in these bogies were driven, the 4th one spinning freely. The 5th bogie, a 4 wheel variant at the very rear, was also powered. The engines could produce 6,000 hp.
This system meant the M1s had no cylinders, and, thus, fewer moving parts than a typical steam engine. So their designers believed the engines would need much less maintenance and could operate as far as 1000 miles without servicing.
All of the M1s were built to pull the C&O's streamliner, the Chessie. It was supposed to be a state of the art passenger train, complete with playrooms for the children, and a lounge with an aquarium. The M1s couldn't wait for the day they pulled their first run of the new train.
To promote the M1s, Margaret was chosen to go on a tour of the C&O system, but it was here that problems started to arise.
All 3 M1s suffered from a long list of teething troubles, the biggest of which was their turbines, which couldn't bear the bumpy rides common on railroads. The traction motors were often fouled with coal dust, and short circuits due to water intrusion from the boiler also contributed to the M1s list of problems.
The Chessie wasn't doing too well either. The fish in the aquarium weren't adapted to life on a train, and often died due to the vibrations. There was also a significant ridership decline. This forced the C&O to cancel the Chessie before it could ever run.
After the cancellation, the M1s were useless. The C&O, wanting to recover form their embarrassing try at competing with diesel, sold all 3 M1s for scrap in 1950. Their engines had only existed for 2 years.
The Rise of the Scrapper
Mary escaped the scrap yards in the dead of night within days of arriving. Saddened by the loss of her sisters, upset at the cancellation of the Chessie, and angry at the diesels for stealing their titles and riders, Mary vowed revenge.
During her escape, a mechanical arm, originally an experimental piece of scrap yard equipment, had fallen into her bunker. Now, the exposed wires on both Mary's bunker and the arm were coming into contact. She used the arm to improve the connection and soon gained control of it.
For the next 10 years, Mary roamed from scrap yard to scrap yard, building more arms, and repairing herself with whatever she could find. By 1960, she had 10 of these arms, 4 in her bunker and 6 in her body. She was now ready to strike.
Mary's Reign of Terror
Starting in 1960, diesels began mysteriously disappearing from American railroads. They were usually by themselves when they vanished without any apparent trace or reason. The managers dismissed these disappearances, as they could always build replacements, but the diesels began spreading rumors of something a bit more scary, that something was destroying diesels relentlessly. Many tried to find this thing, but the few who found it never came back, fueling the growing fire that was becoming the story of the Scrapper.
Mary wasn't happy with her new image. She had hoped her campaign would be a quiet one, and she feared she would be hunted down the moment she was discovered. The only good news was, at the moment, she was destroying diesels faster than they were being build, but she knew she wouldn't be able to keep up her success for long. The humans had decided that diesels were the way forward, and they were producing them at overwhelming rates. Mary would need allies, and soon.
As 1960 became 1961, Mary was searching a scrap yard for replacement parts for her boiler when she heard a loud scream. She investigated, and found a pair of small shunter diesels moving a small 2-6-4 steam engine into a scrap siding. Mary fell pity for her and decided to help. Minutes later, the diesels were scrap metal and she was shunting the steamer, known as Morgan, to an abandoned scrap yard. Morgan felt she couldn't thank her savior enough, and decided to help her in her quest.
Like Mary, Morgan had had a distaste for diesels from the start. She had ben built a few years before Mary, but had a much better career transporting weapons and supplies to East Coast ports during World War 2. As diesels became more popular, Morgan found herself with less and less work. She was unwillingly retired in 1950, but refused to accept diesels as the new rulers of the rails. Now her owners had a bunch of useless steam engines rusting in their yards that needed to be gotten rid of, so they sold Morgan and all their other steam engines for scrap, which brought Morgan and Mary together.
Mary wasted no time outfitting Morgan with her own set of mechanical arms, which were concealed in boxes on each side of her boiler. Mary gave herself more arms, increasing her total to 30. With Morgan by her side Mary continued her rampage throughout the 60's and 70's. By the early 80's however, diesels were being built much faster than they were being destroyed. It was clear the campaign had failed, but Mary and Morgan refused to admit defeat. There was still one place they could try and strike at : Sodor.