A Dangerous Interest by Angela Stranger

Rating: ⭐️⭐️⭐️⭐️⭐️

Lord Andrew Pine decides to forgo squandering family funds to make a fortune in banking—otherwise known to high society as trade. To keep his promise to his mother, he becomes a silent partner to keep the family name out of the business.

When the Duke of Hartwick considers investing, he sends his sister, Lady Jane, to inspect the ledgers. Andrew quickly finds himself distracted by Lady Jane, who proves both intelligent and beautiful.

The story shifts at the Langmores’ annual house party, where the host is poisoned and Andrew's co-partner is shot. Lord Andrew and Lady Jane team up to stop a bank run and uncover why someone wants the institution destroyed.

I deduced the culprit near the end, but the ultimate motive was a sad, genuine surprise. Regardless, the chemistry between the leads carries the story, turning a plot about balance sheets and murder into a solid financial mystery.