The Locked Room (Dr. Ruth Galloway 14) by Griffiths Elly

Pandemic lockdowns have Ruth Galloway feeling isolated from everyone but a new neighbor—until Nelson comes calling, investigating a decades-long string of murder-suicides that’s looming ever closer, in USA Today Elly Griffiths’ penultimate novel in the beloved series.
Three years after her mother’s death, Ruth is finally sorting through her things when she finds a curious relic: a decades-old photograph of her own Norfolk cottage—before she lived there—with a peculiar inscription on the back. Ruth returns to the cot­tage to uncover its meaning as Norfolk’s first cases of Covid-19 make headlines, leaving her and Kate to shelter in place there. They struggle to stave off isolation by clapping for frontline workers each evening and befriending a kind neighbor, Zoe, from a distance.
Meanwhile, Nelson is investigating a series of deaths of women that may or may not be suicide. When he links a case to an archaeological dis­covery, he breaks curfew to visit Ruth and enlist her help. But the further Nelson investigates the deaths, the closer he gets to Ruth’s isolated cot­tage—until Ruth, Zoe, and Kate all go missing, and Nelson is left scrambling to find them before it’s too late.