A Spinster's Guide to Danger and Dukes (Ladies Most Scandalous #3) by Manda Collins

It's the third book in Manda Collins’s Ladies Most Scandalous series! To wed or not to wed? That’s the fake marriage trope question! A little mystery plus a lot of romance will help solve this riddle of the heart

It is a truth universally acknowledged that a lady in danger must be in need of rescue, but whether she wants to be rescued is up for debate—for fans of Evie Dunmore and Netflix's Bridgerton from the bestselling author of A Lady's Guide to Mischief and Mayhem!
 
England, 1867: Miss Poppy Delamare is living a lie. To escape an odious betrothal, she fled to London where she’s been hiding as the unassuming secretary Flora Deaver. However, when her beloved sister is accused of murder, Poppy cannot leave her to the wolves. Only a most unexpected—and unwelcome—collision interrupts her journey home . . . 

Despite a rather dismal first meeting, Joshua Fielding, the Duke of Langham, has no intention of abandoning a lady in need. But he’s not above asking a favor. A fake betrothal will give Poppy and her sister the power of the dukedom and protect Langham from the society misses intent on becoming his duchess.

Yet the longer the ruse goes on, the more Poppy and Langham realize how false their first impressions were—and the less pretend their engagement feels. But before Langham can propose in truth, their search reveals a tangled web of lies and betrayals. With time running out, can Poppy and Langham find the real culprit—before Poppy becomes the next victim?