The Blue Cat Club looked like something out of the fifties, with a blue neon cat very imaginatively stretching across the lintel of the blue-painted door, and the name in equally electric blue flashing over a darkly-tinted plate glass window. As they went inside, Kate somehow expected to be met by a wave of blue Galloise smoke, but knew in her mind that since the laws had changed regarding bars and work places, if she'd found anyone with a cigarette in their hand she'd have been duty bound to arrest them. Still, it did seem like there was something missing, although perhaps she'd seen one too many old films set in post-war Paris.

It was early, so there were only a couple of patrons in the place, lounging in chairs against the wall, listening to the piano player picking away at a tune up on the small stage, a spotlight on him.

Rick moved through the tables to the front, stopping just to the side, his eyes on the pianist, his hands thrust deep into his pockets, head nodding gently in time to the rhythm that only appeared every now and then. She stepped closer to get a good view of the man playing.

He was much more what she expected. Probably around sixty or so, his black skin shone in the light, while a small pork pie hat was pushed back far enough on his head to reveal close-cropped white hair. He wore a suit that was a size too big, and an open-necked shirt with a vest beneath. His foot was massaging the pedals as his fingers, large and knotted, stroked the keyboard.

As he finished, he didn't even look up to see if anyone would applaud, which they did, although it was almost lost in the size of the room. Instead he reached for a drink sitting on top of the piano.

"You drop that inside, it might improve your playing," Rick said genially.

The man grinned and lifted his head slowly. "Castle. Ain't seen you around here in a month of Sundays."

"I've been," Rick defended himself. "Just because you haven't noticed me …"

"Not my fault." The man raised a hand towards his face.

Blind. He was blind, Kate suddenly realised. His eyes were whitened, scarred, and they weren't focusing on anything at all.

"Nor mine," Rick added.

"So what do you want?"

"Do I have to want anything?"

The man chuckled. "Usually. Even if it's only inspiration."

"Oh, I have that," Rick said, glancing at Kate.

"But you're leaving out the best part." The man sniffed, taking a deep lungful of air. "Hyacinth. Not strong enough to be perfume, so soap, maybe. Which means, unless you've changed the habits of a misspent lifetime, I'd say we're in the presence of a lady."

"Maybe I've started dabbing it behind my ears," Rick joked. "But you're right." He half turned. "Kate, I want you to meet the man with the knowledge about anything jazz. He knows more than any dozen so-called experts you care to name." He paused, as if waiting for a drum roll. "Gilbert Brockridge, known to all and sundry as Brock. Brock, this is Kate Beckett. My partner."

The black man held out his hand. "Pleased to meet you."

Kate took it, finding it surprisingly soft and warm. "Mr Brockridge."

"Brock. Please. Else I won't answer."

"Brock."

"Good." He lifted her hand to his lips, just brushing across them before letting go. "Police?"

"Yes."

"Pity. Still, I bet you're beautiful."

"Oh, she is," Rick put in. "Not your type at all."

Brock smiled. "Ain't that the truth." His sightless eyes turned towards her. "You think I'm a cliché, don't you, Detective?" he asked.

"A bit," she admitted. "Although there's nothing wrong with that."

He smiled, then launched into a perfect rendition of the Grieg Piano Concerto, playing for perhaps a minute before ending with a flourish. "And now?" he asked.

"I'm impressed."

"You're supposed to be." Holding up his hands, he moved his fingers in a wave motion. "Classically trained, at least for a while," he admitted. "And now they take a song apart and put it back together in ways the author never intended." This time when he laid his hands on the keys the music was something familiar, but it took a few seconds to realise it was 'Happy Birthday to You'.

Fascinated despite herself, Kate asked, "Can you do that with anything?"

"Honey, if it's got notes, I can mangle it." He chuckled. "So what can I do for you?"

Rick glanced at Kate, who shrugged. Normally she'd have taken the lead in any interview, but for the moment she was content for him to ask the questions. Maybe if she gave him enough rope, he'd hang himself, she told herself. Although there was always the possibility he liked being tied up. She suppressed a lip twitch at the mental image.

Rick nodded and looked back at Brock. "We wanted to talk to you about Merrick Canfield."

Brock smiled wider, showing even, white teeth. "Ah. The fearless quartet leader."

"That's the one."

"What's he done?"

"Is he likely to have done anything?"

"Rick, you first came here as research. You keep coming back because you like my company. And maybe the music. But this is the first time you've wanted to talk about someone still alive."

Rick didn't want to give too much away, so just said, "It's … possible."

"Then I suggest we go take this someplace else." He stood up, and there was movement under the piano. A large German Shepherd, all shaggy fur and feet, appeared at Brock's side, nudging his leg gently.

"Hey, Zulu," Rick said, going down onto his heels to fondle the big dog's ears. "How're things going?"

The dog made an odd noise in the back of his throat, and rubbed his face against Rick's hand.

"He says he's getting old," Brock said, reaching for the harness handle.

"Aren't we all." Rick grinned and spoke to the dog. "But some of us will be handsome forever."

"He just likes you because you used to feed him treats," Brock pointed out.

"He was cute. I always feed cute things. Ask Alexis." Rick straightened up.

"And tell her I want to see her in here before too long." With just a little pressure on the handle from his master, Zulu led Brock off the stage and towards the back of the club.

"This place? Not until she's at least thirty," Rick vowed. "With a bodyguard."

Brock laughed and clicked his fingers.

"Boss?" A man dressed in a silver striped waistcoat and ebony shirt appeared. "You need anything?"

"Yeah. Get Tucson on the stage – he's going to do a set while I sit with my friends here."

"Sure thing, boss."

"And drinks. The usual for Rick and me, and …" His head turned towards where he somehow knew Kate was. "And for the little lady?"

Normally she would have bristled at being called such, but this time she let it pass. "Nothing for me."

"No, now, you have to. Else Nelson here will bring you champagne. On the house." He grinned.

Kate was amused. "Are you flirting with me?"

"Of course." Brock chuckled.

"You think I'm bad?" Rick said. "Everything in a skirt that comes in here is fair game, as far as Brock's concerned. That made for a fun time when a couple of big men from Scotland were visiting our fair city."

Brock's laugh spun through the club. "Good times. Ah, all those good times." He sobered a little. "Now, come on. I'm guessing a white wine spritzer. On the dry side."

"No, really, I can't," Kate said. "I'm on duty."

"Then at least make yourself at home." He waved Nelson away and slid into a booth, Zulu at his feet.

Rick took off his heavy coat and laid it across the back of a chair before joining him. Kate perched herself on the outside edge, unwilling to get too comfortable.

"Brock, last night," Rick began. "Canfield was here, yes?"

The black man nodded. "Surely was."

"All evening?"

"From about seven thirty."

"How can you be sure?" Kate asked.

Brock lifted his wrist to show her his watch. "Just because I can't see doesn't mean I don't know the time." He touched a small knob on the side of the face, and the crystal lifted, allowing his sensitive fingertips to feel the hands. "You can get 'em now that have a kind of digital Braille," he explained. "But I like the old-fashioned sort."

"So I can see."

For a moment she wondered if he'd take offence at the unintentional wordplay, but he just smiled. "Kate, if people watched what they said around me all the time, they'd never speak to me." He stopped as Nelson brought their drinks, then added, "Anyway, yes. Seven thirty. I like to keep an eye on how long everyone performs, so to speak, just in case the natives get restless."

"And did they?" Rick asked.

"A little bit." Brock took a sip from his whiskey. "Normally he plays like a man who's seen too much suffering, and has to get it out of his mind before it sends him crazy. I mean, he's a nice enough guy off stage, but … last night … well, it was like he was only going through the motions. There was no real passion there. I got the feeling he could have reproduced that music any time."

"Isn't that the point of music?" Kate asked. "To be able to replicate it?"

"No. Almost exactly the opposite. A good jazz player never plays a piece the same way twice." He shook his head ruefully. "Of course, there are other schools of thought on that matter, but my personal opinion is that how a man plays is dependent on what he's seen that day, who he's conversed with, even how his morning coffee was. An almost infinite variety of possible combinations, and that makes for the differences. But like I said, I could be wrong."

"But you don't think you are."

"No, I don't."

Rick leaned forward, playing with the whiskey glass but not drinking from it. "Had Canfield ever played like that before?"

"Couple of times." Brock shrugged. "I guess even rich folk have bad days."

"How about earlier in the week? Maybe Wednesday, or Tuesday?"

Brock shook his head. "He wasn't here. He only ever plays weekends, and then only if he hasn't got a classical gig. In fact, he was here the previous Sunday, and played like a man possessed. Man, I have never heard him like that before, and to tell the God's honest truth, I'm not sure I want to ever again. Whatever had happened to him that day, either he was the happiest man alive or he was expecting the end of the world. Didn't like to ask which." He took another mouthful of alcohol, letting it swirl around his teeth and swallowing before adding, "Anyway, last night, he was here, either on stage or propping up the bar. He got a call around midnight, and his playing improved a bit after that, but he was here until gone one in the a.m."

"How can you be so sure?"

"He wears this cologne, should be banned. Smells like something my grandma used to use to polish up her nick-nacks. Every time I passed by I could smell it. Even made Zulu sneeze." As if he knew he was being talked about, the German Shepherd stirred under the table, turning around once before settling again.

"So he didn't leave?"

"Nope. Ask Nelson. He was serving him most of the time, and he told me Canfield was a morose son of a bitch. Not like his usual self at all."

Rick glanced at Kate. "Not his usual self."

"But like I said, we all have our off days."

Nelson reappeared. "Boss, phone call for you."

"Who is it?"

"Lorna Michaels. From the Soho Music Times."

Brock seemed pleasantly surprised. "Maybe I'm gonna be famous after all," he said, getting to his feet.

A guilty look had flashed across Rick's face, and Kate sighed.

"Another of your conquests?" she asked as she stood up. "How do you keep track of them all?"

"Electronic notebook," Rick replied, following suit. "Names, ages, dates, favourite positions … just imagine what your entry says."

Brock laughed before she could make a suitably pithy comeback. "You don't change," he said. He reached forward, and managed to take Kate's hand in his. Bending forwards, he kissed her knuckles again. "And you, dear Kate, are welcome any time."

"Thank you. I think."

She tried to pull away but he kept hold, a frown crossing his forehead as he rubbed the back of her hand with his thumb.

"You know, it was odd." He spoke slowly, thoughtfully. "We shook when he left, and I'd swear he'd cut his fingertips."

"What?" Kate was now all ears. "What do you mean?"

"It's a rookie thing to do. Most bass players have calluses, from plucking the strings all day and every day. But he felt … well, like he'd worn grooves in them."

"Boss," Nelson said again. "Ms Michaels?"

"Go tell her I'm coming." He let go of Kate's hand, his scarred eyes still facing her direction. "And when you're ready, you come back and tell me what this is all about." He took hold of Zulu's harness and they followed the barman.

"How did he know I was police?" Kate asked, watching the man walk away back towards the office, his guide dog at his side.

"Brock used to be a bad guy," Rick explained as he shrugged back into his coats. "He lost his sight to a drive-by thirty years ago, and he always says it was the making of him. He went back to the piano, found not being able to see meant he could feel the music better, and … here he is. I guess he can still sniff out a cop." He laughed. "Especially when she wears hyacinth."

She ignored the last comment. "He's certainly a character."

Rick nodded, grinning. "That he is."

"No, I mean it. The jazz pianist in Serpent's Tooth … that's Brock, isn't it?"

"I keep forgetting, you have my entire output." Rick looked smug as he opened the door for her before stepping out into the cold air. "It's so nice to have a fan."

"I was younger. Much younger."

"Are you saying I'm old?"

"Would I do that?"

"Yes."

"Well, even you can't turn back the clock, Castle." She strode along the sidewalk towards where they'd parked the car, knowing he was at her heels.

"What, and miss out on all these amazing experiences?" He shook his head. "Never in a million years. Besides, I think that was very informative."

She glanced at him. "You mean the way he gave Canfield an alibi we already knew about?"

"Not that. I mean the way he talked about the man. Twice in as many hours someone's described him as being two people."

"So?"

"Come on, Kate. You've got to agree that's significant."

She turned on him. "No, Castle, it's not. As interesting as that was, it was a waste of time I don't have. I'm supposed to be solving the mystery of the diamond necklace theft, not traipsing around after you trying to prove something that's … unprovable."

"There's no such word."

"I don't care. For all I know the man might be schizophrenic, and maybe he hasn't told us everything, which by the way is pretty par for the course, but he didn't kill Michelle Tyler, and he didn't rob the Sheikh."

"But you're going to look into his background."

"What I do or don't do is none of your business." She carried on walking, fishing in her pocket for the car keys.

"Kate, I know you. I know what you're feeling. And I know you think Canfield's connected with the deaths, and by extension with the robbery. You're beginning to think like me, Kate."

She stopped suddenly and he walked into her, even as she turned, her face like stone. "I do not think like you. And don't you ever suggest it again."

"Yes you do. And it's burning at you that you can't prove it. The fact that Canfield has such a solid alibi that it's almost like he arranged it that way." He was so close he could smell the scent of hyacinths, just as Brock had detected. "Tell me it's not true."

Whatever she might have replied was lost as the shop window shattered behind them, showering them with shards in a glittering cascade a moment before the sound of the gunshot registered.

With an admirable speed for a man of his advancing years, Rick took hold of Kate and threw her to the ground behind the car as two more bullets thudded into the vehicle's side. Then there was the sound of an engine revving, rubber squealing on the road surface, and all was quiet.

Until Kate said, "Can you get off me so I can draw my gun?"

Rick looked down at them both, his hips pressing into hers. "Oh, yeah. Sorry." He rolled to one side.

She pulled her pistol from its holster, edging above the hood of the car so she could see. "Damn," she muttered. "Long gone." She stood up, eyeing the smears of burned tyre tread on the road. "CSU might get something, though." She took her cellphone out and speed-dialled the precinct.

Rick slowly got to his feet, aware of the gathering crowd of passers-by, and went to brush the tiny fragments of glass from his coat when he stopped. "Wait a minute," he murmured. There was something on his hand where he'd been holding her arm. Something wet. And sticky. Angling his hand to the light so he could see, it looked … red.

He stared at the blood on his fingers. "Kate. You've been hit."