The jigsaw puzzle that Duval (François Cluzet) is seen doing, is of Rembrandt's 'Jeremiah Lamenting the Destruction of Jerusalem'.
Duval being hired to perform a menial and seemingly pointless administrative task, working alone in an empty office space, is very similar to the establishing plot of the Sherlock Holmes story "The Adventure of the Red-Headed League", in which pawnbroker Jabez Wilson is hired by the fictitious League to daily attend an otherwise empty office and copy out pages from the Encyclopedia Britannica by hand.