In 2015, Aaron Statham - a very successful marathon runner in the past - goes missing on his wedding day. The police are convinced that the young man has disappeared of his own free will and close the inquiry. Only his fiancee Lisa doesn't believe that Aaron is capable of betraying her, she is convinced that something horrible has happened to him. A year later, having exhausted all other means, she turns to the small "H&W private investigation agency", run by an eccentric 62-year-old Lady Arina Holroyd and her junior partner Luke Weir, to find out the truth. The case of the missing marathoner is not as straightforward as it seems at first glance, nor how it is dealt with by the police. It turns out to be a much more complex and increasingly dangerous murder investigation. The nearer Arina and Luke get to the bottom of it, the more obstacles they meet on their way. The killer is clever and heartless, he removes anybody who gets in his way, he doesn't leave any trace behind. One after another the key witnesses are murdered or disappear without a trace. The killer is exceptionally smart, he covers up his tracks well and, like a shark, he is approaching from the deep gloom ready for the next merciless attack.