The sheer audacity of Russia's chemical-weapon attack on the U.K. can be traced through the journey of a small — and fake — Nina Ricci Premier Jour perfume bottle.

It contained Novichok, a lethal Soviet-era nerve agent, and was smuggled from Russia into Britain on a regular Aeroflot flight. Landing at Gatwick Airport — used by more than 45 million travelers a year — it passed through London Victoria and Waterloo train stations and a budget hotel on its way to Salisbury, a sleepy medieval town in southern England.

There, in broad daylight on a Sunday afternoon, it was sprayed onto the door handle at the home of a former Russian spy, Sergei Skripal.