John is an introverted man who designs puzzles and is happy to live alone without any interruptions from the outside world. When he gets a phone call from his sister-in-law Lucy (Anna Maxwell Martin) his entire life changes.

Lucy asks John for help. He reluctantly goes to her house where she informs him his twin brother James is missing. This brings back memories from his past when his father left the family and the twins looked on as their mother was confused and hurt.

If John can take the place of his lookalike brother and unobtrusively go to his office perhaps he can retrieve a notebook that might give them a clue as to what happened to James. The thing is, James is a detective chief inspector and John has no idea what a detective really does. But he agrees to the plan with the idea of walking into the police department, going to James’ office and retrieving the notebook.

On the surface, this sounds easy, even though John is not sure he can pull it off. And once he gets to the office he is immediately wangled into a murder investigation even before he gets to look for the notebook. This nervous and eccentric man goes along with his ruse for fear of being found out. He also fears impersonating a police officer will land him in jail.

What is interesting about his ruse is that John uses his puzzle solving skills to actually solve the case. His team is impressed but there are a couple officers in the department who are leery of John, aka James. There’s something different and strange about him.

At the end of the day after solving the murder, John manages to locate James’ notebook and returns to Lucy. What they discover is that the notebook is in code and John must figure out a way to decode it. Perhaps if he does, that will give them a clue to what happened to James.

When Lucy learns John intends on continuing the ruse and returning to the Police Department the next day, she is confused. After all, he is a man who does not interact well with others. But he is determined to locate his missing brother, and besides, he actually enjoys solving crimes.

Each day brings a new crime for him to solve, to the amazement of the others. Who would have thought that an introverted puzzle-maker could actually be a great detective?

Assuming the identity of his brother actually affords him the opportunity to delve into a world he had never seen or understood. And he is forced to confront his inner issues as well.

This is an intriguing series. There are six episodes in the first season. The final episode answers many questions but also poses new ones to be solved in the next season. The show began streaming Thursday on BritBox.