Benjamin Franklin and a Case of Artful Murder (Benjamin Franklin Mystery)

Lord Shenstone has insisted that Cavitty, a local artist, paint a portrait of his wife prominently displaying the famous Shenstone diamond. Lady Shenstone leaves the coveted family heirloom with Cavitty so he can study it for the painting, but when she returns to retrieve it, Cavitty claims that he does not know what has become of it.
Desperate to find the diamond and not let her husband know of its absence, Lady Shenstone turns to Benjamin Franklin, the American investigator working abroad in eighteenth-century London. Franklin delves into the case, coming across many eccentric characters from whom he must discover the truth of the diamond's whereabouts.
The latest in the Ben Franklin series, A Case of Artful Murder is narrated by Franklin's apprentice, Nick Handy. Though Nick is only thirteen years old, his resourcefulness and astute intuition serve Franklin well as they land him a job in Cavitty's studio. There he must remain undercover as he witnesses forgeries, murder, and even a taste of romance.