If I am not mistaken, this is the last book from the Liok Siao-hong series. In this book (first published in 1981), the author wanted to tell an incident, the only incident, that made the Sword God smile/laugh. In Liok Siao-hong's world, there was only 1 Sword God, and that was Sebun Jiu-soat. To become a sword god was not an easy matter and that was why the people never saw Sebun Jui-soat smile, thus this story was created. However, after I read this story, I didn't find the incident extraordinary enough to make Sebun Jui-soat smile. It was hardly funny enough to make me smile.
Liok Siao-hong's friend went missing after going to a deserted poor small town to examine something [he was an escort for a shipping company]. Liok Siao-hong went to the small town to find about his friend's fate. During the investigation, he saw the dead body of his friend and felt that his own life was in great danger, because although the town was small and poor, the inhabitants were of interesting characters. Which one of them had killed hid friend? From the clues, it must be someone whom he had really trusted. At the end of part 1, there was a news that Liok Siao-hong had died in the small town.
His friend Beef Soup (I have no idea why Beef Soup became his friend. In the previous book, Beef Soup was his enemy.) went to Sebun Jiu-soat's house to ask for his help. Because he was the number 1 swordsman, she thought the Sword God could handle Liok Siao-hong's enemies in the small town. But the enemies were too clever and both Beef Soup and Sebun Jiu-soat fell into their hands. The whole thing was the bad guys's scheme to rob a shipment of gold passing through the little town. Liok Siao-hong also didn't die because of the help of his friend Sukong Ti-sing, the king of thief and a master of disguise. The disguise thing was very interesting to read and it was clever enough to fool the clever bad guys... and made the Sword God smile.
As for the murder mystery, the conclusion was similar to the Murder on the Orient Express.