Part 1

At 11:43 p.m., Elise Mercer was standing in the hallway of the apartment she shared with her husband, Nathan, holding a mug of tea that had gone cold. She was thirty-six, wearing an oversized white T-shirt and navy sleep shorts, and waiting for a man who had told her he was working late.

Nathan arrived at last. At thirty-nine he had perfected the weary smile that made strangers forgive him before he spoke. Tonight, however, Elise saw a hotel key card slip from his coat pocket and land beside her bare foot.

“I thought you were at the office,” she said.

He looked at the card, then at her. “It isn't what you think.”

“Then tell me what it is.”

His phone lit up on the console. A message appeared from a woman named Mara: You said you would tell her tonight.

Nathan reached for the phone. Elise set her mug on the floor before she could drop it. “How long?” she asked.

“Please let me explain.”

“That wasn't the question.”

He stared at the key card. “Three months.”

Elise had imagined a confession might arrive with shouting. Instead there was only the hum of the refrigerator and a knock at the apartment door. Nathan went pale. “She wasn't supposed to come here,” he said.