The Night Gate by Peter May

The body of a man shot through the head is disinterred by the roots of a fallen tree.

A famous art critic is viciously murdered in a nearby house.
Both deaths have occurred more than 70 years apart.
Asked by a forensic archaeologist in Paris to take a look at the site of the former, Enzo Macleod quickly finds himself embroiled in the investigation of the latter, and two narratives are set in train - one historical, unfolding against a backdrop of real events in Occupied France in the 1940s; the other contemporary, set in a France going back into Covid lockdown in the autumn of 2020.

At the heart of both is da Vinci's Mona Lisa.

Tasked by de Gaulle to keep the world's most famous painting out of Nazi hands after the fall of France in 1940, 28-year-old Georgette Pignal finds herself swept along by the tide of history. Following in the wake of the Mona Lisa as it is moved from chateau to chateau by the Louvre, she finds herself both wooed and pursued by two Germans sent to steal it for rival patrons - Hitler and Göring.

What none of them know is that the Louvre has secretly engaged the services of the 20th century's greatest forger to produce a duplicate of the great lady, one that even those who know her well find hard to tell apart. The discovery of its existence is the thread that links both narratives. And both murders.