‘This looks to be the place,’ said Jack, having been directed by a goldsmith on Cheapside to a miniaturist portrait shop along Gutter Lane. The four of them stood outside a crooked little building tucked between a milliner’s and a bookseller’s. In the leaded window were a selection of small, blank, oval pieces of vellum and card, and some sample lockets.

They entered the shop’s cramped confines. As their eyes grew accustomed to the gloom, they noticed a young man bent over a desk, painting by candlelight. He appeared to be copying a miniature portrait, stroke by stroke, and didn’t stir from his work.

After a while, Jack coughed into his hand.

The young man looked up, startled. He had pale skin, curly black hair and a wispy moustache. ‘My apologies,’ he said. ‘Nathan Holme at your service. How can I help you?’

‘Nathan Holme!’ whispered Yori, nudging Jack excitedly. ‘The same initials as the portrait!’

Jack hurriedly got out the locket and showed it to the miniaturist. ‘Tell me, is this your work?’

The artist took the locket, cradled it gently in his palm and inspected the portrait under the glow of the candle. His watery eyes widened in surprise, then a sad smile passed across his lips. ‘I’m afraid not … that’s the work of my father, Nicholas Holme.’

‘Can we speak to your father?’ asked Rose eagerly.

Handing back the locket, the young man mournfully shook his head. ‘My father passed away last month … the bloody flux …’ With a heavy sigh, he turned back to the two miniature portraits on his desk. ‘I’m trying to match his style, but I never could master his technique. It’s so elusive … his lightness of touch … the freshness he gave to his subject’s countenance … the way he captured their features so gracefully …’

‘I’m truly sorry for your loss,’ said Jack earnestly as he attempted to regain the young man’s attention. ‘I know what it means to lose a father. But I’m hoping not to lose a sister as well.’

Nathan paused mid-stroke.

‘She’s missing,’ Jack went on, ‘and this locket is the only lead we have to her. Do you know who commissioned your father to paint this portrait?’

Nathan put down his brush and pulled out a leather-bound book from the desk drawer. Opening it, he ran a finger slowly down the lines of scrawled black ink. Jack waited impatiently, trying to decipher the handwriting upside down and garner a name. Nathan flicked to the next page, found only a few entries, tutted irritably, then snapped the book shut.