The first call came from the school nurse at 10:17 on a Tuesday morning.

“Mara, it’s Caleb,” the woman said. “He collapsed during gym class.”

By the time Mara Ellison reached Briarwood Elementary, an ambulance was already parked beside the curb.

Her six-year-old son lay on a stretcher beneath a thin gray blanket. His face was pale, his dark hair damp against his forehead. His identical twin brother, Toby, stood beside him clutching Caleb’s blue backpack with both hands.

“I’m okay, Mom,” Caleb whispered.

He always said that when he was frightened.

Mara climbed into the ambulance with both boys and held Caleb’s hand all the way to St. Anne’s Children’s Hospital.

She told herself it was dehydration. Caleb had skipped breakfast. He had been tired lately, but first grade had been a difficult adjustment. Children got dizzy. Children fainted.

Children recovered.

But the emergency physician did not look reassured after listening to Caleb’s heart.

“There’s a murmur,” she said. “Has anyone mentioned that before?”

Mara shook her head.

The doctor ordered an electrocardiogram, blood work, and an echocardiogram. Two hours later, Caleb was admitted for observation.

Toby sat on the edge of the hospital bed, placing toy dinosaurs in a line across Caleb’s blanket.

“You can have the green one,” he said. “He’s the strongest.”

“I like the blue one.”

“The blue one’s fast.”

“I need fast more than strong.”

Mara turned toward the window so the boys would not see her face.

A nurse entered and explained that a pediatric heart surgeon had been asked to review Caleb’s scans.

“His name is Dr. Julian Hart,” the nurse said. “He’s one of our best.”

The door opened a few minutes later.

The man who stepped into the room was tall, with dark brown hair, tired gray eyes, and a narrow scar near his left eyebrow.

Mara stopped breathing.

The folder slipped from her hands.

Across the room, Toby dropped the plastic dinosaur he had been holding.

Caleb pushed himself upright.

For several seconds, no one spoke.

Then Toby reached for the front pocket of his brother’s backpack.

“Mom,” he whispered, his face turning white. “Why does that doctor look like Dad?”

Dr. Julian Hart froze.

Toby pulled out a small photograph with bent corners. He carried it everywhere, though Mara had asked him more than once to leave it safely at home.

The picture had been taken nearly seven years earlier at a lake outside Columbus. Mara stood in the center, laughing as a man wrapped his arms around her from behind.

The man in the photograph had Julian’s face.

The same mouth.

The same nose.

The same gray eyes.

Even the same faint scar near his eyebrow.

Julian took one step closer.

“Where did you get that?”

“It’s our dad,” Toby said.

Julian stared at Mara.

She moved between him and the boys.

“I don’t know who you are,” she said, “but that man’s name was Michael Rowan.”

Julian’s gaze remained on the photograph.

“No,” he said quietly. “It wasn’t.”

Mara’s fear hardened into anger.

“I was married to him.”

Julian looked up sharply.

“What did you say?”

“I said he was my husband.”

The room seemed to contract around them.

Julian approached Caleb’s bed slowly. He introduced himself, though his voice was no longer steady, and asked permission to examine him.

When he pulled the collar of Caleb’s hospital gown slightly aside to place the stethoscope against his chest, he saw the birthmark.

It was a pale crescent near the boy’s left collarbone.

Julian stared at it so long that Mara touched his wrist.

“What is it?”

He stepped back.

“Does Toby have the same mark?”

Mara did not answer immediately.

Toby tugged down the collar of his T-shirt.

The crescent was there.

Julian closed his eyes.

His twin brother Gabriel had been born with that exact mark. Their mother used to call it his little moon.

Julian had one too, though his was smaller and rested closer to his shoulder.

The surgeon looked again at the photograph.

The man beside Mara was wearing a watch Julian recognized. Their father had given it to Gabriel on their twenty-first birthday. On his right hand was the silver class ring Gabriel had refused to remove even after college.

Julian had not seen either object in more than nine years.

“That man wasn’t Michael Rowan,” he said.

Mara’s hands curled around the bedrail.

“Then who was he?”

Julian looked at the two boys, then at the woman who claimed to have married his dead brother.

“His real name was Gabriel Hart.”