“He asked me to keep an eye on the place.” She avoided meeting my gaze. “I did, of course. I’d come over every week to make sure things were just as you’d left them. One day I noticed a file box, one of those cardboard thingies, flimsy but solid enough to hold household files. It was on your kitchen table. I’m ashamed to admit I snooped. It belonged to your mother. Contained her financial and medical records, bonds, and her marriage certificate.”

I thought about the day we cleaned out my mother’s house. I remembered Tim carrying a box to our car, but I didn’t recall ever seeing it again. “What did you discover? Was my mom one of those secret millionaires?” I forced a lightness into my tone that I didn’t feel.

“I don’t know about her financial holdings, they’re none of my business.” Mary studied her hands, resting on the tabletop. She seemed particularly interested in her knobby joints. I knew my neighbor well enough to tell she was lying. Mary’s intense interest in my life convinced me she’d likely studied every cent that had gone in and out of my mother’s accounts. I pictured a spreadsheet of Mother’s income and expenditures tacked to Mary’s musty cellar wall. I’d tackle that issue later.

“What did you discover?”

“There were numerous medical bills from her office. Dozens—maybe even hundreds—of patients’ medical procedures from the late 1990s.” Her brow creased as she looked at me. “Odd items to keep. I was immediately suspicious. Remember, I made a living investigating insurance claims. I could sniff out fraud.”

“Fraud?” My eyes went wide. “My mother was a by-the-book person. I don’t think she...” I thought about the damaging pills she’d forced on me as a little girl. I pictured her hand smashing the metal thermos against my dad’s temple. I began to shake. If she could kill her husband and poison her only child, she could certainly wheedle money out of insurance conglomerates.

“There are many ways to commit health-care fraud without patients knowing it,” said Mary. “The most common is double-billing?—”

“Yes, the doctor submits multiple insurance claims for the same service,” I interrupted. “I know all about this, Mary. I was a medical biller. The other popular strategy is phantom billing?—”

“Charging for services never rendered,” cut in Mary, her crooked pointer finger raised in the air. “There’s no way to tell whether these bills are duplicates or completely bogus, but something’s not right about them. If everything was on the up and up, Lilith—your mother—would have no reason to keep them.”

Something in my brain notched into place. I could almost hear the clicking. “The fire.”

“What fire?”

I spoke slowly, explaining, “When my doctor’s office tried to access my childhood medical files, they were told about the fire in old Doc Gleason’s office. Nearly all the files were destroyed.”

“How convenient.” Mary grinned. “Funny how your mother knew to keep these specific files.”

I sighed. It wasn’t funny. Not at all. Was there no end to my own mother’s deceit? “She must have kept the records so she wouldn’t triple-bill the insurance companies and create a red flag. This was all before the wide-scale use of computers.”

“I suspect someone was onto her, and that’s why she kept the files. Maybe so she could show that Dr. Gleason had made her do it, or something,” said Mary. “But what did it matter all this time later, and her dead? It didn’t make much sense for Tim to keep the files, so I took them home and looked them over.”

“Why would you do that?” I narrowed my eyes, searching her face.

She flushed. “I didn’t plan to take action against her estate, Caroline. The statute of limitations on a fraudulent insurance claim is six years and the records were from the nineties.” She raised her hands in front of her as if to ward off a physical attack. “I just wanted to discover...”

I looked at her reddening face, for once not finishing her sentence for her. She rubbed a hand across her lips.

“What did you hope to discover by scouring those records, Mary?” If she’d been as uninterested in my mother’s financial holdings as she claimed—something I didn’t believe—then her interest in the medical files was personal.

“Nothing, really.” She looked down.

“That’s a fib. We both know it. You were hoping to find a clue to my mother’s intent—to figure out how her mind worked,” I guessed. “So you could link her behavior to mine, root out the reason I killed my baby?”

“No, that’s not true.” She met my narrowed eyes, her own wide. “I know you accidentally killed Emmy. Tim said so.”

Her words arrowed into my chest like a dagger. “Then what?” My voice was husky with the emotion I was trying to contain. “You wanted to figure out why Tim sent me away?”

When she clamped her lips together, I had my answer. She wanted to know just how dangerous I was. If the neighbor she needed so desperately would ever harm her. I couldn’t blame her, could I? Given the opportunity, I’d likely do the same thing. I thought about my mother’s deviance. How much was transmitted through the genes? Was I a garden-variety criminal like my mother had appeared to be, or had nature supercharged my DNA, making me a cold-blooded baby killer? Had I even fooled Tim? Apparently, Mary had wondered about these things too.

“There’s more,” said Mary.

I looked at her and, once again, she didn’t meet my gaze. “Lilith also had her medical files, and yours, in a small folder tucked among the phony claims.”

I thought about Dr. Ellison telling me someone had dropped off our files at the hospital just two days earlier. Mary. “Why didn’t you just tell me about all this?”

“How could I? When I took the files, you were institutionalized. I couldn’t even tell Tim without admitting I stole them. When I went back to your house the next week to return them, the file box was gone. I had to keep them or risk him knowing I’d helped myself to your private information.”

I didn’t say anything for a long time, letting my eyes go out of focus as I thought about Mary’s admission. Eventually, I looked at her. “Did you read our medical files?” When she nodded, I did too.

“I knew I had to give the information to your doctor, but I was afraid to be implicated. I mean, I’d stolen your medical records, Caroline. That’s a felony. But when I realized how much you were suffering, I knew I had to share them. It took me a long time to do it, and I’m sorry I was such a coward.”