“Nicki, I would never tell Lee anything you’ve told me in confidence,” Mel said solemnly.

I felt better when I heard those words. I thought, Good. I’m covered. Little did I know that, six months later, Mel would summon me for an important chat and explain that, from now on, I wasn’t allowed to tell her anything that she couldn’t share with Lee. She would continue to keep any secrets of mine that had gotten in before the deadline, but this was the cutoff point: I was forbidden from confiding in her in future, unless it was something I didn’t mind Lee knowing about too.

“The thing is, we kind of . . . are already seeing each other,” she went on hurriedly, keen to get it over with now that she’d finally taken the plunge. “Lee’s asked me to move in with him and . . . I’ve said yes.”

“Oh. Well . . . congratulations.”

“Are you sure you don’t mind?” Mel asked.

I hadn’t said I didn’t mind. I had said, as tactfully as possible, that I did. Or I thought I had. I minded the manipulation: the fiction that they cared how I felt about it, and that their relationship was no more than a vague notion at this stage, awaiting my approval. I later found out that before she’d called me, Melissa had confirmed her booking of the moving van that would transport her possessions to Lee’s flat the following Friday.

Do what you have to do, and indeed have already done, I should have said, and if I want to tell you how I feel about it, that’s up to me.

“It’s fine,” I reassured Mel instead. “I hope you’ll be very happy together.” This is the thing about deception that some people forget: its practitioners don’t do it solely for their own sakes. Often they do it to make others happy. It’s embedded in the training program we liars go through: we see that when we tell the truth, our instructors scowl, raise their voices, turn red in the face. Anyone who cares more about pleasing other people than about their own happiness—anyone who believes, deep down, that everyone else matters more than they do—learns fluent dishonesty at a young age.

I swallow the last of the tea in my mug. Something inside me cracks and gives way. I can’t keep up my brittle act any longer. “What’s happened to us, Mel?” I say.

Her eyes widen at my use of the old nickname.

“Does it really have to be this way?” I will not cry. Will not. “Look, we can’t change the facts—I’m a reprehensible slut, and you’re a self-righteous prig who imagines she has to tell her husband everything, even things about his sister that are none of his business—but can’t we accept each other’s shortcomings and get beyond them? I’m sorry for asking you to lie to the police. Don’t do it if you don’t want to.”