On a typical rainy evening in London, Detective John Carter got a call from the Metropolitan Police asking him to investigate the theft of a valuable painting from The National Gallery that had some historical significance. The painting belonged to a private collector who had just loaned it to the gallery for an exhibition. John quickly reached the gallery and started investigating. He found the CCTV footage that clearly showed a man wearing a black coat and a hat entering the gallery when it was about to close. He was seen holding a small toolkit. John found footprints of the same man in the storage room where the painting was kept. The puzzle had just begun.
He started collecting evidence from the gallery and spent the whole night interviewing the staff. He discovered that the painting was insured for a substantial amount which led him to believe that it was an inside job. After examining all the evidence, he narrowed it down to James, the museum's security guard, who showed a keen interest in the painting. However, when he checked the footage, James was seen doing his regular rounds at the time the painting was stolen.
John had hit a dead end when he received a call from an anonymous source who told him that the painting was seen in the back of a moving truck headed towards the docks. John went to the docks and found the truck. When he approached the driver, he saw that it was James, the security guard, wearing a black coat and a hat.
John immediately arrested James and searched the truck. He found the toolkit that was used to remove the painting from the wall. James pleaded innocence and said that someone had threatened to harm his family if he didn't do what they asked him to do. John wasn't convinced and he knew there was more to this than just an inside job.
John decided to go deep into the case and started investigating the painting's history. He found that the painting was commissioned by a wealthy businessman, Richard Blake, who was murdered soon after the painting was completed. It was believed that the painting held some sort of a clue that could help in catching the killer but it was lost in the time. The painting has been missing ever since and its reappearance had become very important for the authorities.
John knew that the only way to solve the case was to find the killer of Richard Blake. He started looking for his descendants and found that Blake's son, Charles was living in Australia. He contacted him and explained the purpose of his visit. Charles was reluctant at first but later agreed to meet John.
John flew to Australia and met Charles who told him about a diary that his father had left him. The diary had some clues about the killer and the lost painting. They deciphered the codes in the diary and found that the killer was Richard's former business partner, Edward.
John flew back to London and arrested Edward who finally confessed to the murder and stealing the painting. He had been hiding it all these years and had finally decided to sell it as he needed the money.
The painting was returned to the private collector and the case was closed. John had solved one of the most mysterious cases of his career.