The Necklace Affair (English for "L'Affaire du Collier") by the Belgian artist Edgar P. Jacobs was the tenth comic book in the Blake and Mortimer series.

The necklace of Queen Marie-Antoinette that was believed to have been destroyed centuries ago has been found by Sir Henry Williamson, a wealthy British collector based in France.

Blake and Mortimer arrive in Paris in order to testify at the trial of their sworn enemy Colonel Olrik only to learn that he has managed to slip away under the very noses of the police during a transfer to the court house from the main jail.

They barely manage to save the jewel case from the strongroom, but when they open it the necklace is gone and they find a note in which Olrik claims responsibility.

Blake summons his contact Commissaire Pradier of the DST, the French security service (similar to the FBI or MI5) who is in charge of the Olrik case.

In the morning, Blake and Mortimer are visiting Duranton when they witness an attempt by Olrik's men, led by his henchman Sharkey, to kidnap him.

With the help of Vincent, Duranton's loyal valet, Blake and Mortimer manage to rescue the terrified jeweller, but, in spite of the sudden arrival of the police, Olrik and his men escape, again via the catacombs.

Arriving at his hide-out he switches on the TV: during the programme Mortimer announces that the necklace Olrik obtained from the park is in fact the fake.

Meteors and The Time Trap, it forms the final instalment of a trilogy of adventures that take place in France featuring many of the same characters—Blake, Mortimer and their contact Pradier.