PLATTSBURGH, N.Y. A small favor for a killer's daughter. A stolen kiss and a furtive sexual encounter. And ultimately, sneaking tools past guards for use in an audacious escape from a maximum-security prison.

Such were the moments in Joyce E. Mitchell's evolution from a workaday prison employee to a love-struck and fully aware accomplice, as outlined in three statements Ms. Mitchell made last month to investigators.

Ms. Mitchell, 51, pleaded guilty on Tuesday to assisting Richard W. Matt and David Sweat, two convicted murderers, in their elaborate breakout early last month from the Clinton Correctional Facility in Dannemora, N.Y.

"I was already bringing stuff in to him, and didn't really feel I could stop," she said, adding that Mr. Matt assured her that "they were getting out, and we were all going to be together."

The escape set off a three-week manhunt before Mr. Matt was shot and killed on June 26 and Mr. Sweat was shot and captured on June 28.

Officials have offered ample details about the inmates' plans and the law enforcement pursuit, and Mr. Sweat himself has bragged about his role in the escape. But the central question of what drove Ms. Mitchell, a soft-spoken married woman, to help the prisoners has only now been answered.

Her statements to investigators sketch a vivid chronology of how Ms. Mitchell, a former supervisor in the prison's tailor shop, came to commit her crimes by falling for a prisoner, eventually succumbing to the seemingly irresistible momentum and dark excitement of the escape scheme.

Ms. Mitchell was meant to be the getaway driver. She was to meet the two men at midnight near a powerhouse outside the prison, but she had a panic attack and did not show up. That panic may have been caused by threats made by the two men directed at Ms. Mitchell's husband, Lyle, whom the inmates nicknamed "the Glitch," and whom they planned to drug and murder.

"Inmate Matt was going to kill 'the Glitch,' " Ms. Mitchell said.

Her confession was first reported by NBC, and the statements were obtained by The New York Times through a Freedom of Information request. They reveal how deeply involved she was with the men and how detailed their escape plan was.

Ms. Mitchell, for example, was meant to drive a Jeep, with four-wheel drive, "because the place we were going was in the woods." She was also meant to bring an array of supplies for the escape, including tents, sleeping bags, GPS, money, a cellphone and "fishing poles."

Mr. Matt also asked Ms. Mitchell to "bring a shotgun that he could saw off," she said.

The plan was to hide out somewhere six to seven hours from Dannemora "until it quieted down." Then, after about a week, she and Mr. Sweat would continue to hide and Mr. Matt would go on his own. "I was caught up in the fantasy," she said. "I enjoyed the attention, the feeling both of them gave me, and the thought of a different life."

But while she said she liked Mr. Sweat, her primary affections were undoubtedly for Mr. Matt.

"Each time he would ask me for a tool, I would go to the store and get them," she said on June 8, two days after the escape.

The statements, which were given on June 7, 8 and 10 to investigators including federal agents and the New York State Police, show the seduction of Ms. Mitchell by Mr. Matt, who had dark, rakish good looks and a charming demeanor, according to officials and Ms. Mitchell.

"Inmate Matt and I got along well," Ms. Mitchell told investigators on June 7, just a day after he and Mr. Sweat were discovered to be missing. "We talked every day and he treated me with respect and was nice to me. He made me feel special."

Mr. Matt and Mr. Sweat both worked in sections of the prison's tailor shop, although Mr. Sweat had been separated from Ms. Mitchell in September after prison officials suspected "an inappropriate relationship." She, however, denied having romantic feelings for Mr. Sweat, 35.

Mr. Matt, though — who had killed two men, including his former boss, whom he dismembered — was different. In late 2013, Ms. Mitchell began doing errands for Mr. Matt, who was then 47, calling his daughter to check whether she had received a painting he had made. (He was an amateur portraitist.)

Ms. Mitchell admits knowing it was wrong but began regularly contacting the daughter, who was grateful. "She was glad her father had someone on the inside who was looking out for him," Ms. Mitchell said.

Last November, Ms. Mitchell asked Mr. Matt to paint a portrait of her three children as an anniversary gift for her husband, who also worked in the prison tailor shop. In exchange, she bought the inmate a pair of boxing gloves, though he did not finish the painting in time. Other presents followed: cookies, brownies, pepper.

But the requests took a more suspicious turn, as Mr. Matt asked Ms. Mitchell to buy two pairs of spectacles, equipped with lights, which the two men apparently used as they worked at night, unnoticed by corrections officers. (A dozen employees at the prison remain on administrative leave in the wake of the escape.) Mr. Matt offered an innocent explanation for the glasses: He and Mr. Sweat merely wanted to paint at night.

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The relationship and plot quickly intensified. In late April, Ms. Mitchell said, Mr. Matt suddenly "grabbed me and kissed me" with an open mouth. (Shortly after that, he asked for a screwdriver bit, which Ms. Mitchell bought and gave him.)

In May, he asked for oral sex, and she consented; she also groped his genitals in several instances, using a large prison coat to disguise their activities.

Ms. Mitchell also said that she took sexually charged photos for Mr. Sweat and wrote him provocative notes, but that she did not have sexual contact with him.

In May, Mr. Matt asked for — and received from Ms. Mitchell — hacksaw blades, which the prisoner initially said were for making frames. But that ruse was soon abandoned.

"Inmate Matt was coming into work tired," Ms. Mitchell said. "I asked him about sleeping, and he said he was up all night. After a couple of days, he told me he and Inmate Sweat had cut the holes and were going down in the pipes." She said the two men had also found tools in a toolbox and "were using them to get out."

A June 10 statement gave hints of the subterfuge Ms. Mitchell and the inmates used to evade detection. The hacksaws were hidden in frozen hamburger — Mr. Matt told guards it was for goulash — and transported in an envelope that also contained tubes of paint. "So if the bag went through the metal detector, they would think it was the metal tubes of paint," she said.

Later, chisels and a punch were smuggled into the prison the same way, she said.

Ms. Mitchell also began making phone calls for Mr. Matt, disguising her identity by pretending to be a hospital employee. The point of those calls was not clear, but Ms. Mitchell soon learned that the men had chosen a day to break out: June 5.

"He told me that they were getting out tonight and we were all going to be together, me, him and Inmate Sweat," she said. "He told me to pick them up in Dannemora."

But Ms. Mitchell's resolve weakened as the day progressed. After leaving work and having dinner with her husband, "I was not feeling well," she said. By 10 p.m., she was in a hospital emergency room; she later was admitted, leaving Mr. Matt and Mr. Sweat — by then on the loose — to fend for themselves.

The police began calling the next day, June 6, as the manhunt began in earnest. She was interviewed that day and lied to investigators.

But by June 7, the day of her first statement, she swore she was telling the truth about her role in one of the nation's most flamboyant prison breaks.

She faces two-and-a-third to seven years in prison as part of her guilty plea.

"I am," she concluded, "really sorry for what I have done."