As spring approaches, Sherlock is persistently searching for a new adventure, a new investigation, to occupy his brilliant mind. So, as a game, Irene suggests to her friend to engage with a series of strange and unexplained events happening in London. And indeed, Sherlock's logic identifies common points and a bizarre, invisible thread that connects them... After successive surprises, the trio of friends, Sherlock, Lupin, and Irene, will come face to face with a mysterious, highly intelligent criminal. To what thrilling revelation will their investigation lead?