In the Money With You by Edie Cay

Prudence Cabot sailed to Europe to find a lover.
As an American widow flush with cash, she has hopes of finding the burning, passionate love she never experienced in her marriage. But instead, she found The Ladies Alpine Society, and is now pressed into planning a fundraising ball with the expedition’s accountant, Leo Moon. Prudence feels out of her depth, but glad to have a partner-in-crime to help her navigate British culture. But the taciturn Mr. Moon doesn’t like her—or does he like her too much?

One look and she saw right through him.
Leo Moon is not his real name. He has spent most of his life building his wealth, protecting his mother, hiding in plain sight. But in walks Prudence, and his secrets are laid bare. When he overhears her talking about wanting a lover, he offers his services. After all, they’ve been charged with planning a ridiculous party, so they have an excuse to call on one another. But as they keep their burning-hot secret, Leo’s past waltzes into London, and Leo is forced to choose.