''Which suggests it was me who delivered the ultimatum, doesn't it?"
"If that were true, why was Sam so keen to accept it?"
Her eyes narrowed warily as she tried to see the point I was making. "What makes you think he was?"
I shrugged. "Because he couldn't sign up to your fabricated alibi quick enough. He was even happy to rope Jock into the lie if it meant he could distance himself from you. Not that your husband minded," I said with an ironic glance in Jock's direction, "because he didn't want his Tuesday evenings with Sharon made public. But why would Sam go along with it unless he had something to gain? There were any number of reasons he could have given for being in your house that night-none of which were remotely suspicious. Looking for Jock, being one."
"Why ask me?" she demanded. "Sam's the one who lied. All I did was tell the truth, which was that I'd been at home all evening, waiting for my husband. And I didn't have to pretend I was alone either because the police made that assumption themselves. It's not my responsibility if Sam decided to sign a statement saying he was at your place when he wasn't."
"Except he says you didn't give him any choice. According to him, you phoned him at his office the next morning to say the police were asking about people's movements the previous night because they were looking for anyone who'd seen Annie. You then told him you'd dug him out of a hole by saying he and Jock had been at our house from 7:45 and it was down to him to persuade Jock to support the story. You said I'd never suspect he'd been with you if it was your husband who gave him an alibi. And you were right, I didn't."
"This is Sam's version, presumably?" she murmured sarcastically.
"Yes."
She glanced at my rucksack again. "And there's no statement from an earwigging telephone operator to back it up?"
"No."
"Then you can believe what you like, and the police can believe what they like." she said indifferently. "Sam's always going to put his own gloss on it-he wouldn't be human if he didn't-but he's the one who lied and I'm the one who told the truth. And I'm damned if I'll let him put the blame for his perjury on to me."
I nodded as if I agreed with her. "Fair enough, but you'll need to be ready for police questions about who proposed what and when because Sam's revised statement says the ideas came from you-in particular his and Jock's alleged sighting of Annie at 7:45." I paused. "According to Sam, that was your suggestion. You told him the police wanted proof that she was staggering about in the road earlier in the evening, and if he gave it to them they'd call it an accident and the whole bloody mess would go away."
I was lying, of course-Sam had never denied that the reason he mentioned Annie was to get himself out of the hole he'd dug with me when he told me she was drunk-but Libby didn't have a monopoly on invention, and it was fascinating to see how rapidly her control deserted her when she was accused of something she hadn't done. In a horrible sort of way, she reminded me of Maureen as she hissed and spat her furious denials. We were all shits ... ganging up on her because we didn't like her ... making Sam out to be the victim ... trying to shove responsibility on to her...
"Why would I have suggested anything so bloody stupid?" she finished. "Supposing the police hadn't believed Sam and Jock? Supposing we'd all had to admit what we'd really been doing that night? Why would I tell him to say he'd seen Annie just before the one period in the whole evening when we both had a cast-iron alibi? It's ridiculous. They'd think we were in collusion to cast suspicion away from ourselves. I'd never saddle myself with anything so unnecessary."
I studied her for a moment. "But why would you even worry about collusion?" I asked curiously. "Surely all you knew when you phoned Sam the next morning was that Annie had died outside our house at 9:30? How does that make mention of her stupid and unnecessary?"
She sobered rapidly. "Sam told me you were saying it was murder."
"Not true," Sam countered fiercely. "I was so ashamed of leaving the poor woman in the gutter that I steered clear of the whole blasted subject. All you and I discussed that morning was how to avoid saying that I'd been with you."
She gave an angry smile. "Then maybe I'm talking with hindsight, but it's hardly the point at issue. You're accusing me of inventing an absurd lie when anyone who focused attention on themselves by saying they'd seen Annie that night was a fool ... particularly if they were trying to hide an affair. You may be that kind of fool, Sam, but I'm certainly not."
"That's very true," I said before Sam could fire off again. "I've always thought how clever you were to keep your story simple, claim absolute ignorance and offer no alibi at all. All you had to say was: I can't help you ... I was home alone from five o 'clock ... didn 't hear anything ... didn 't see anything ... didn't go anywhere. You could repeat that till you were blue in the face because there was no one to contradict you except Sam. And once you'd muzzled him, you were safe as houses, because if the police had caught you out in a lie, you'd have shrugged and said, you were only trying to keep the affair secret."
"I didn't need an alibi," she said.
"No," I agreed, "but only because no one saw you with Annie at 6:30. I presume you bumped into each other in the road, and she started calling you a 'dirty tart' again. But why the hell did you have to go out at all, Libby? What was it for? To buy some booze in the hopes of putting Sam in a better mood? Or maybe you needed it yourself because you were boiling mad about being given the elbow? Is that why you lost your temper with Annie so quickly? Because you were angry that Sam had made it clear he'd rather stay with his wife than play stud to a bored tart who hadn't got the gumption to get up off her backside and find an identity for herself that didn't involve exploiting men? Why couldn't you stay in your sordid little bed and weep for your own inadequacies instead of killing Annie because she dared to point them out to you?"
Caution smoothed the planes of her face turning it into a practiced mask. "Don't be ridiculous," she said. "What's 6:30 got to do with anything?"
I took a printout of her e-mailed statement from my pocket. "It's the time you gave in here, so presumably it's important."
She made another dismissive gesture. "I've already said I'll go with Sam's version, not mine. Are you going to crucify me for making a mistake?"
"Your worst mistake was to have a bath and start washing your clothes," I said, "but I suppose you had her blood on you. The postmortem photographs prove you went for her like a madwoman."
"Oh, for God's sake!" she said wearily. "I assumed Sam and I were going to make love, so of course I had a bath. And it wasn't my clothes I was washing-it was sheets."
I tapped the e-mail. "Then why didn't you put that in here? Why pretend otherwise?"
She managed a creditable laugh. "Because I forgot. In any case, I wouldn't have let Sam in at all if I'd had anything to hide."
"You couldn't afford not to. He'd already told you over the phone that he was going to confess everything to me that evening if you didn't agree to end it."
"It was over anyway. Why should I care?"
I looked at Sam. "Because you were afraid he'd tell me Annie knew about the affair. He says she was always accosting you in the street calling you a 'dirty tart.'" I touched my toe to the rucksack. "There's a letter in here from Michael Percy, describing how you lashed out at her with your shopping bag and ended up on the ground, arse over tit. And you wouldn't want me adding you to the list of people with grudges against Annie." I finished, "not if you'd just left her for dead in her house."