"So…what did you get from him?" I asked, as our cab picked its way through the mid-afternoon traffic and pedestrians.

"Well, as I said he was highly intelligent and soft-spoken."

"Unlike many gardeners."

"Only if you're stereotypical," Sherlock replied airily, which instantly made me realise how my comment must have sounded and regret it. "Besides, it's not an ideal climate to graduate into just now. "

"What did he say?"

"Not a lot. He liked Molly, she wasn't interested. He did have a criminal record and a history of violence. I tried my best to make him tell me exactly what it was he had done, but he wouldn't do it. I told him it would look bad for him if he refused to answer, and he said he didn't care; they'd already made up their minds about him. Besides, he said, if he did tell me he would only blacken the name of another, far more influential person, which would do nobody any good since this person was far more trusted than he was. I asked him if he knew anything about what had happened to Molly too."

"And…?"

Sherlock craned his neck to see the road ahead. "He said Molly was dead."

What little hope I had begun to build based upon Sherlock's conviction died away with that information. And yet Sherlock's eyes were keen and bright. "Well, there you go," I said quietly.

"Hmm?"

"He was there at the lighting of the bonfire. He must have seen the remains go on. Which logically suggests he was there when it happened."

"When what happened?"

"When Molly was..." I tailed off, lest I strike a nerve.

"Molly's not dead."

"For Christ's sake, what more proof do you need?"

"The rest of Macfarlane's story, for a start." I waited.

"Apparently Macfarlane was first employed in November as the gardener, after graduating from Oxford – as a sort of stop-gap. His mother once knew Greenwood. He said Greenwood was convinced he owed her a favour, and wanted to repay that favour by watching out for her son. Anyway, Macfarlane couldn't find work, so he was kept on. Well, then he got a part-time job as an assistant in a law-firm, which one time involved taking a trip out to the hospital to talk to a client. That's where he met Molly, and they became friends. This led to Macfarlane going over to Bart's more often, but when he expressed a love interest, she started fobbing him off, which made the friendship awkward. Anyway, Macfarlane had mentioned Molly to Greenwood a couple of times, but had no idea that Greenwood was Molly's godfather until she turned up for tea at the end of February. And Jonas Greenwood apparently had a talk with them both and told them that they had better reconcile their friendship, as he hoped Molly would be round more often and he didn't want either of them to feel awkward in each other's company. And he made them shake hands, like little children after a fight.

"Well, Macfarlane was still head over heels in love with Molly, but she wasn't interested. So he contented himself with her friendship, and seeing her when she came over for tea. That's why he stopped looking for law jobs – because he was happy enough gardening. Then, according to him, last evening he arrived later than usual to Greenwood's house. Nothing was out of the ordinary. Macfarlane had been cutting back the hedge, as well as replacing the garden gate and repairing the window frames with putty, and there was a large pile of things to be burned. Jonas Greenwood brought him a coffee and set a match to the first pieces of debris. He then told Macfarlane to slowly build up the fire and then go home – he could manage the rest. Besides it was getting on for seven, and that was when Macfarlane usually went home anyway. The first Macfarlane heard of the murder investigation was in the morning, when the police came to his house to arrest him."

"And you believe him?"

Sherlock looked at me as though I had gone mad. "Well of course, why wouldn't I?"

"Why would you?"

"Because as a lawyer if he'd wanted to lie about the case he'd have been more than able to do it in way that would convince the police, or at least get them talking. But he didn't try and fight the accusation, showing that if he was the murderer then he had very little imagination. And yet if he did lie then his whole story, which fits together perfectly, would have been made up on the spur of the moment for the police, and that shows a great deal of imagination. Therefore if he lied he was simultaneously showing very little imagination and lots of imagination, which is stupid to suggest. Therefore in all likelihood he was telling the truth."

"So…why are we going to Blackheath?"

"I want to talk to Macfarlane's mother and find out why somebody might want to frame him."

-/-/-/-/-/-/-

The house of Isabelle Macfarlane was a bungalow. Squat, grey and with minimal garden space, there was something terribly precise and yet, at the same time, strangely lonely about it. As though somebody had been so careful to keep it perfect that they had in the process drained it of any personality.

James Macfarlane's mother, on the other hand, was anything but drained of character. She was small and curvy, with flaxen hair, piercing grey eyes, wore a blue fur-lined top, a tight black skirt and high heels, and had blue eyelids and jewellery to match her top. As soon as we told her we were here about her son's conviction, she was up in arms. "Now look," she said in an over-enunciated accent, with an uncomfortable edge to her voice, "I know my James. I don't care what scientific evidence is pinned on him, or what you police-detective people – whatever you are – think, but my James didn't do this. Come in if you must and have coffee. I'll tell you anything if it will help end this silly farce."

To my surprise, Sherlock accepted, motioning me to sit down and do the same. I have never seen someone make coffee in such a flustered, angry manner. It wasn't simply the manner of someone worried for her son; it was the manner of someone who's pride had been acutely hurt. Sherlock noticed it too – as I saw from the way his intrigued eyes tracked her back and forth between the kitchen and the living room.

As soon as she had furnished us with coffee, she stood over us and fixed us with a determined gaze. "Whatever happened to that poor girl, mark my words it will have that creep Greenwood behind it." Behind Sherlock's feigned bafflement was acute interest, certainly, but another expression – one teetering on the brink of futility. "Why? " he asked, "Do you know him?"

"Do I know him?" She gave a hoot of derisive laughter. "Huh – do I know him alright." Were it not for the hard, cold, steely line that her mouth had become, I might have thought I saw a hint of softness creep into her eyes. "We were best friends once. Or rather he was my best friend and I was his only friend. And then we were lovers." She took an emery board from her breast pocket and began to file her nails. It certainly seemed to me as if this was a distraction-behaviour; that she was doing it in order to avoid having to watch us or focus on herself. "But…then I fell in love with another man – Matthew." She nodded at a picture hanging on the wall of a clean-shaven young man with shoulder-length brown hair, brown eyes and wearing a red shirt. He had an easy, honest, open smile on his face. "Matthew is James's father. You couldn't have met a lovelier person on all of God's green planet…" her voice trailed away as she became absorbed in memories. Sherlock twitched in impatience.

"So what happened?" I prompted, before Sherlock could cut in with a remark that would spark yet more snappy anger.

"Well, we married. On my last night as an unmarried girl Greenwood and I met up. I gave him a photograph of the two of us, to remind him of the good times we had had together. He seemed grateful at the time. So I settled down with Matthew, and I got pregnant. We got a house together, and old Greenwood was left on his own. He deserved it. I'd always stuck by him and forgave him for his faults. Nobody else would go near him. I mean, the man didn't take much care of himself, he had a foul temper, he hardly ever spoke and he was very, very paranoid." I couldn't help thinking at this point that this woman was incredibly two-faced. Here she was pretending to be good friends with this man, whilst all the time loathing him and quite possibly saying so to everyone behind his back. No wonder Greenwood was paranoid. "And he was the most disgusting little voyeur when he was jealous," she continued with repulsion. I glanced at Sherlock and saw that the hope and interest had gone from his eyes. "I was always looking over my shoulder when Matthew and I were together. When James arrived he backed off a bit. So everything went smoothly until James was sixteen. Then Matthew fell from a ladder mending the roof and broke his neck." She swallowed and pulled a handkerchief out from her sleeve. "It was a freak accident, but it left me alone in the world with a child to raise.

"Now, as you can see I am not the strongest of women, easily preyed on by more cunning people. It was about then that Greenwood showed up. After all those years he'd still been monitoring me from a distance, and now that I was free again he was going to seize the opportunity. He was nice enough at first. In the intervening time he'd become the well-loved, well-regarded man he is now. Now, I, being the forgiving type I am, invited him for supper, and that night, then and there, only one month after my husband's death, he proposed to me. Naturally I was shocked and said no, and he insisted, getting onto his knees and proclaiming his love. Then he tried to kiss me. Well, I'm no doormat so I slapped him. And he…" she gasped and turned pale, "…He grabbed my wrists, and I screamed and James came running in. He'd always been a timid, peaceful boy until then, but he wasn't going to stand to see his dear Mum being treated like that, so he broke a chair over that freak's head. Then he knocked his lights out." Her cheeks were blazing now and her eyes were burning with pride.

"And what did you do after that?" Interrupted Sherlock.

"I hugged him and told him how proud I was of him, and told him what a pervert Jonas Greenwood was, and all the grief he had given me over the years." She glared at our feet. "James paid for it with a criminal record. We tried to protest, but as I said Greenwood already had far too good a reputation. Pinning the blame on him would be like claiming the Pope tried to molest the Queen. They simply didn't believe him. The papers are saying he has a history of violence but you – you know the truth don't you? You know his intentions were noble!" She stared imploringly. "Please clear his name for me. I can't live without him, you know."

"Well," Sherlock said, standing up and handing his now empty mug to Isabelle. "This has been a very helpful visit. Thank you for your time, Isabelle."

"I've helped clear my James's name then?"

"Nope," said Sherlock, straightening his scarf, "Actually you've strengthened the evidence against him considerably. But you've answered another important question I had, so not to worry." Sherlock made a move towards the door but Isabelle Macfarlane blocked his path, quivering all over. "Explain," she ground out between her teeth.

"The police will say that your extreme pride at his violence may have gone some way to putting him in the position he is in now. Goodbye."

"Wait…one more thing you should see…" she darted past Sherlock, briefly laying a hand on his chest as she went past as an entreaty to wait. When she returned, she was holding a photograph; the one of Greenwood and Isabelle that Isabelle had described being given on her last unmarried night. Except…Isabelle had no face. The face had been roughly scratched away with the blade of a knife, leaving only tattered white paper fibres. "That's how he returned it to me, just after the whole incident occurred," she whispered.

Back in the taxi, Sherlock was strangely quiet and morose. I asked him what was up. "Nothing, I'm fine," he shot back reflexically. Then, on consideration: "I wanted to talk to James's mother because I wanted to prove that he didn't have the character to murder anyone. I got the opposite to what I wanted. It's not proof, and it's not strong evidence, but…" in a rare instance of self-doubt Sherlock trailed off. "Oh, I don't understand!" he burst out in annoyance, just as my phone beeped. "I just know it's all wrong, but the facts all fit Lestrade's theory, and…well…that can't be right! It just can't!" He clasped and unclasped his hands in a paroxysm of conviction. "Who's that?" he added, glancing at me as I scrolled down the text.

"It's Lestrade." I looked up, my heart heavy. "He's been to see Molly's parents." I tried to think of a gentle way to tell him. "The vicar was there as well. Molly was always very fond of you. And apparently her parents want…they want you to read a short piece out at her funeral the day after tomorrow."

"But…but Molly's not dead," said Sherlock, genuinely confused.

"I'm afraid she is," I said, as gently as I could. "The DNA sample from the burnt remains was a perfect match."