In episode 1, when a murder takes place in the sleepy market town of Bakerbury, the local police are baffled by a crossword puzzle left on the body. With their case going nowhere, they turn reluctantly to Cora Felton, a recent arrival in Bakerbury, whose fame as the eponymous Puzzle Lady suggests she can help DCI Hooper and the local police unravel the crossword clue and solve its first murder case.

As Cora throws herself into a murder case that has the town's residents baffled, she starts to gather allies and enemies in equal measure. Tenacious journalist Anton Grant is as much captivated by Sherry, Cora's niece, as he is Cora, while Anton's ex-girlfriend, amoral lawyer Becky Baidwan, might help, or might throw them all under the bus. As Cora's team assembles, it becomes apparent what they lack in experience, they make up for in attitude.

But the eccentric Cora isn't who she claims to be. And while she digs into a cold case she thinks may be connected, she uncovers a dark truth behind another young woman's death. Cora puts herself in the killer's sights. Which is a dangerous place to be…