Fifty years ago, the glorious Honeychurch Hall estate made headlines as the scene of a botched train heist that left two men dead and the whereabouts of a chest of diamonds unknown. So when the daughter of the signalman on duty that night asks antiques dealer Kat Stanford to value her father's railway memorabilia, Kat jumps at the chance. But the collection contains more surprises than Kat could've imagined, and soon it's full steam ahead on a very modern-day murder investigation. Meanwhile, Kat's mother Iris is wrapped up in the writing of her latest steamy novel; estate manager Delia is preoccupied by the upcoming grand opening of the Hall's Polar Tearoom; Kat's beau, local detective Mallory, is spending far too much time with his impressive ex, Chief Superintendent Stella Greenleigh; and there's a stuffed polar bear on the loose.