Captain Ingram's Inheritance (Rothschild Trilogy #3)

Frank Ingram, an impecunious officer, is seriously wounded at Waterloo. Rescued by Lord Roworth, he meets Roworth's sister, Lady Constantia, an angel of mercy. Despite their different backgrounds Connie loses her heart to Frank, and is delighted when a surprise inheritance transforms him into an acceptable suitor. But Frank and Connie are each hiding a terrible secret they are sure will ruin their chances for marriage to anyone - let alone each other.