Roseann Sdoia was standing at the metal barricade, in front of Forum, watching the Marathon, when the second bomb went off.

The first thing she saw, after the smoke cleared, was a detached foot, clad in a white ankle sock.

“Was I wearing socks?’’ she asked herself. “Is that my foot?’’

It wasn’t. But her own right foot wasn’t doing so well either, hanging on by shreds of flesh, and pouring blood. She was bleeding to death.

She sat up on the sidewalk. It was madness.

“Will somebody help me? Please?’’ she pleaded, but her words sounded strangely muffled to her, because her eardrums had been blown out.

A Northeastern student, a kid named Shores Salter, grabbed her by the armpits and carried her onto Boylston Street. A doctor, Collin Stultz, appeared at her side. He told her she’d be OK. And then he told Salter to pull as hard as he could on the belt that they’d put around her right thigh.

Shana Cottone, a Boston cop, bent down and put her face right above Roseann’s and said she’d be all right. Cottone asked her if she had been there watching her husband run the Marathon.

“What the hell does that have to do with anything?’’ Roseann Sdoia, single and proud of it, snapped back at her.

And that was good. Because that was the old Roseann. All spit and vinegar.

They put her on a backboard, but there were no ambulances. All the ambulances were full. A Boston Police wagon pulled up. It was no ambulance, but it would have to do.

They loaded Roseann and Marc Fucarile, whose right leg had been blown off, into the wagon. Mike Materia, one of the Boston firefighters who carried her to the wagon, jumped in the back. The doors closed, the darkness fell, and the stench rose.

Materia pulled hard on the tourniquet and tried to comfort her.

He used his body to keep her from sliding off the metal bench as the wagon picked up speed and peeled around corners.

“Please, please, please,’’ Roseann asked him, “hold my hand.’’

Her hand was badly burned, oozing, and Materia worried about her getting an infection from the grime on his, so he grabbed her wrist instead.

“No!’’ Roseann objected, hitting him in the chest. “My hand! My hand! Hold my hand!’’

He grabbed her hand and gently squeezed.

It was quiet and dark and bumpy.

“Am I going to die?’’ she asked him.

“No,’’ Materia told her, softly.

They got her to Mass. General, and saved her life but not her leg.

The days passed and Materia kept coming back to her hospital room, to see how she was doing. Roseann’s mother was smitten.

“Oh,’’ Rose Sdoia told her daughter after he left one day, “he’s adorable.’’

Roseann’s sister and her girlfriends were just as bad, a Greek chorus, going on about the tall, handsome firefighter who helped save her life.

Roseann was mortified.

“I can’t believe you people,’’ Roseann cried. “I just got blown up, and you’re all trying to fix me up?’’

But the firefighter kept coming to the hospital, and the truth was Roseann wanted him to.

One day, sitting in her hospital bed, she turned to him and said, “You know, you are way too young for me to date.’’

A smile spread slowly across Mike Materia’s face and he said, “I don’t remember asking.’’

Roseann laughed. A loud, hearty Roseann laugh. It was the first time she had laughed since the bombing.

She put him in her iPhone contacts and typed “Matt’’ instead of “Mike.’’ With her broken eardrums, she heard “Matt.’’ And he kept coming back, first to Mass. General, then to the Spaulding rehab. After three weeks at Spaulding, she was discharged to return to her apartment in the North End. Outside the hospital, she found that Mike had arranged to bring an engine from the North End firehouse to ferry her home.

She approached Mike on her crutches and for the first time, consciously at least, felt something in her stomach, something that felt like more than friendship. He swept her up, lifting her into a bear hug.

He spent whole days with her while she was being fitted for a prosthetic leg. It was the first time they were alone together. They talked so easily. He carried her purse so she could use her crutches. Some of his firefighter buddies teased him about the purse, but he shrugged it off.

At first, he just wanted to make sure she was OK. But he was drawn to her determination, her work ethic, the way she looked after and cheered up other Marathon survivors, the way she treated people.

Sometimes, Roseann would look at him and think their age gap was too wide. He’s 37, 11 years younger. Were they compatible? He’s reserved. She’s not. But they complemented each other. They made each other better.

She didn’t know if he had the same feelings for her that she had for him. A few months after the bombings, they were sitting at Markey’s Lobster Pool in Seabrook, N.H., having lunch, and it came up in conversation that a reporter from People magazine had asked Mike how to describe his relationship with Roseann.

“What,’’ Roseann asked tentatively, “did you say?’’

Mike shrugged.

“I told her I was your fireman,’’ Mike said.

“And,’’ she asked, “are you?’’

Mike Materia reached across the table and, for the first time since that horrible afternoon in the back of the dark, putrid police wagon, took Roseann’s hand. They were a couple.

Roseann went back to the real estate development firm where she worked and struggled with her new limitations. She sometimes fought the blues. She told Mike that there were all these things she’d never do again, wear heels, wear shorts, wear a bathing suit. So Mike showed up at her apartment wearing a bathing suit, a Hawaiian shirt, and an inflatable toucan around his waist. She laughed. At her lowest, he always made her laugh.

When she woke up in the morning and reached for her prosthetic leg, she would find that Mike had filled it with M&Ms or an orange or some paper flowers.

It was a long courtship. They didn’t want to rush anything, to make sure it was right. They liked nothing better than curling up at Roseann’s apartment with a pizza. Shores Salter, the college kid who held the tourniquet on her leg, and Shana Cottone, the cop who willed her to live, became part of the furniture.

The four of them, their friendships forged in the bloody chaos on Boylston Street, hung out like lifelong buds.

Roseann always wanted to go to Nantucket for the Christmas Stroll, and she and Mike finally made it in December, with their mutt, Sal.

Mike suggested they take Sal for a walk on Jetties Beach. But Roseann begged off. Later, they met a woman who worked at the whaling museum and she offered them a private tour. It was a Sunday morning, and they were up on the museum’s observation deck, looking over the harbor.

Mike bent down and put something on Sal’s collar.

“Did you see the new dog tags I got Sal?’’ he asked.

Mike didn’t pop the question. Sal did. And the question was written on Sal’s new dog tags: “Uhh, he wants to know . . . if, uh, you’ll say ‘Yes?’ ’’

As Roseann was reading the dog tags, Mike got down on one knee. He pulled out the ring he had wanted to pull out on Jetties Beach. It was worth the wait.

Roseann wrote a book about how she and Mike and Shores and Shana came together, the depth of their relationships. It’s called “Perfect Strangers,’’ and it’s a perfect title. It will be published next month, three weeks before this year’s Boston Marathon.

Shana and her longtime girlfriend, Sarah, are getting married, too. It’s not clear who will tie the knot first. Roseann and Mike are shooting for sometime in the fall.

Roseann Sdoia and Mike Materia don’t think of themselves as anything special. But they are. They are the ultimate repudiation of the act of hate that unwittingly brought them together, an affirmation of all that is right and good, living proof that love is stronger than any bomb.

Kevin Cullen is a Globe columnist. He can be reached at cullen@globe.com. Follow him on Twitter @GlobeCullen.