In spite of her previous pronouncements about me—or even because of them—Gretchen seemed at pains to keep me close, to make a show of how unified we were, though she never said that she no longer held me responsible for what I still thought of, absurdly, as the panty incident. In fact, we didn’t talk about it at all, and I suspected some kind of mutual gag order had been decided upon, as if to spare both our blushes. Or because they suspected someone else had been responsible but didn’t want to open that particular can of worms.

It was a fitting image: slimy, repulsive, and stinking of decay.

That’s maggots.

Same difference, at least in this instance.

When I went into the kitchen to get ice for my drink—I had moved on from wine to vodka and didn’t give a shit who knew it—Gretchen came with me. She eyed the basket of crusty bread on the counter, then opened the fridge and lifted out a cucumber, a fat, ripe tomato, a jar of black olives, and a block of feta cheese. The light from the fridge was cold and blue. It hollowed out her fragile beauty and made her waifish.

“Do we have anything less Greek?” she mused, half to herself. “I mean, it’s good and all, but I could murder a pizza.”

“I don’t think so,” I said. “Drink?”

“God, no. I think I need a break.”

I nodded, sipping mine absently while she assembled a rickety sandwich, and suddenly the weight of my past lies was too much to bear and I wanted to be done with it all.

“My sister died a long time ago,” I said without preamble, like I was confessing to a priest in the hope not just of forgiveness but of redemption, the chance to start over.

She looked up, her eyebrows raised, and started to say something puzzled, but I shook my head.

“I know,” I said. “I told you she worked in the movie industry doing CGI. I lied. Sorry.”

She put the knife down and considered me.

“Why?” she said at last.

“I honestly couldn’t tell you. It’s something I do. Did. I’m trying to quit.”

She gave a snuffling laugh. I had meant my confession, but I saw suddenly how it opened a door to ask something in return.

“Gretchen?” I said.

“Don’t ask,” she said quickly. “I know I shouldn’t have blamed you, and I’m sorry, but I didn’t want to talk about it. Still don’t.”

I nodded, but I wasn’t letting her completely off the hook.

“You said we were in danger—”

“I was being stupid,” she said quickly. “Forget it.”

“O . . . K . . . ,” I said.

“Really.”

“One more thing.”

“Do I have to?” she said, not so much defiant as whiny, like a kid being sent for a bath.

“Yesterday afternoon,” I said. “When the rest of us went to the fort and you stayed with Mel.”

She was immediately on her guard, pushing her hair behind her ears as I’d seen her do sometimes when she wasn’t comfortable.

“What about it?” she said, slicing the tomato with more care than was strictly necessary.

“Did you see Brad?”

She put the knife down again and turned to face me, lips pursed and face red, like she was ready to tell me where to get off, but then she deflated and looked at her hands. For a long moment she said nothing, and when she finally spoke her voice was barely above a whisper.

“He texted me,” she said. “Offered to buy me a drink at a hotel in the town center.”

“And you went,” I said.

She checked that no one could hear from the other room, then nodded quickly.

“It was just a drink, right?” she said. “Except that it wasn’t. He had a room. He said he and Kristen were on the outs and maybe I’d like to . . . you know.”

I buried my surprise and just said, “And did you?”

She shook her head.

“I went to the room,” she confessed. “But it all felt too weird. I’m not . . . I don’t know. It’s not my style, you know? I like Kristen, and even though he said . . . anyway, no, I didn’t.” I nodded again, thinking that was the end of it, but then she added, “He was actually quite sweet. And sad. Not like he normally is at all. I actually considered . . . but then . . .”

Her face tightened, all the tenderness that had been there a moment before now turning into something else entirely. Again she checked the doorway and stooped, as if trying to make herself small, before she leaned in and whispered.

“He called me Melissa. Not once. Four or five times. He said I looked like her and being with me would be like being with her. Freaked me out. I mean, I was insulted, you know, because he obviously wasn’t really interested in me, but it was more than that. It scared me. He’s, like, obsessed with her. Asked me to sit like her. Talk like her. I couldn’t deal, so I took off.”

“And he was . . .”

“Not happy,” she said with a bleak smile. “But then you’d already figured that out, huh?”

“Yeah,” I said, thinking of the butchered underwear strewn about her bedroom floor. “I think I had.”

Chapter Thirty-Three

I took a health and environmental science class in college. It was mostly pretty dull stuff, but one of the case studies stuck with me. A Minnesota family in the nineties started getting frequent bouts of what they thought was flu: lethargy, occasional nausea, disorientation, an inability to focus, and memory loss. They were treated and released over and over, with doctors considering chronic fatigue syndrome to be the leading possible cause of their symptoms. This went on for three years. In that time the kids’ grades crashed, the father lost his job, and the mother became so depressed with her failure to complete even simple tasks that she became suicidal. The only time they improved was when they went away on vacation, but as soon as they got home, their symptoms would creep back in. Almost five years after the syndrome began, a random home improvement revealed a leak in the exhaust line of their furnace. Prompt blood tests confirmed that the cause of all their sickness was chronic exposure to low levels of carbon monoxide.

Cases where the dosage was much higher—when people stayed with a running car in the garage, say, or when they used a charcoal stove indoors—had more dramatic and alarming results, frequently leading to unconsciousness within ten or fifteen minutes and death in twice that. The gas is light and odorless. Most people don’t notice it even as they start to succumb to symptoms.

I stare at the hose on the stairs, and I know why we have been so tired, so woozy, so forgetful. I had thought we were being drugged, but we weren’t. We were being poisoned.

Marcus is upstairs. So are Gretchen and Kristen and Brad. I have no idea if they are alive.

I run clumsily to the front door, but it has been locked with a key. I follow the hose down the cellar stairs to the generator, past the scuba gear, not thinking about who might be down here, stumbling and falling on the steps. My skinned knees flare and my shattered left hand shrieks with pain as I land awkwardly on it, but I get up and blunder over to the throbbing yellow generator and shut it off. The exhaust line has been fitted to the hose and fastened in place with pipe grips.

The gas is light. That means it will rise, and the sealed windows of the villa that make it so stuffy will hold it. The second and third stories are now a gas chamber. I look at the scuba gear, but I don’t have time to mess with regulators. Instead I snatch up the small tank of pure emergency oxygen, then turn to the tools and garden implements. I pick up a picklike mattock, but it’s too heavy to wield one-handed. Among the dust and cobwebs is a ball-peen hammer, the kind with the rounded striking head.

That will have to do.

I hit the wall hard with my left shoulder as I navigate the spiral back to the foyer but keep going, breathing as shallowly as I can while I climb. I can’t smell the poison. I can’t taste it. But I know it’s there and that there’s nothing I can do that will keep it out. The air is probably loaded already, which means I have only a few minutes of consciousness. Maybe not even that.

I round the corner onto the landing of the third floor at a ragged trot and make for Marcus’s door. I weave as I walk, listing like a rowboat taking on water, and fall heavily against the door. It is locked. They all will be, a precaution against whoever broke into Gretchen’s room. I set the oxygen tank down but waste no time knocking. There is a good chance they are already unconscious or worse.

I swing the hammer wildly at the door handle, hitting, missing, hitting again, using all the strength I still have. The handle buckles but the latch holds, so I try charging with my right shoulder. The first hit is too close to the hinge, but the second, with a blundering run from the top of the stairs, splinters the wood around the faceplate, and the door judders open.

Marcus is motionless on the bed, wearing the shorts I saw him in the night before, the sheets kicked haphazardly aside, lying on his belly, his face buried in the pillow. He always slept like that. I don’t wait to check his pulse or breathing but stride across the room, hammer raised.