Carlo Salvatore is the "poor rich boy" in the Biggles book of the same title. Carlo, who was twelve at the time of the events in the book, was the only son of Rosario Salvatore, a Texas oil millionaire and one of the richest men in the United States. His father's wealth, did not, however, ensure an easy life for Carlo, even in the best of times.
Carlo's mother had died soon after he was born, and she was, at least partly, the cause of the difficult lifestyle he was forced to lead. Carlo's mother had once been betrothed to one Cesare Paola. Rosario Salvatore, Cesare and his brother Antonio Paola were old friends from the same village in Sicily. In their youth, they had saved enough money to emigrate to the United States. Cesare and Antonio had decided to get rich quick by pursuing a life of crime. Rosario had prefered to walk the straight path and finally ended up extremely wealthy. When Cesare and Antonio had been arrested, they had appealed to Rosario for help, which he refused. Antonio was subsequently executed and Cesare given a long prison sentence. To compound matters, Cesare's fiancee visited the United States while he was still imprisoned. She approached Rosario for help and ended up marrying him. Cesare, on his release, swore to exact vengeance for these betrayals.
As Carlo was Rosario's only son, the millionaire expected that Cesare would strike at him through the boy and so had him heavily guarded. This, unfortunately, gave for a miserable lifestyle. Carlo was not allowed to go out or even go to school. He had no friends and spent most of his time sitting in a room with bullet proof windows. Without much to divert himself, Carlo indulged in his two interests: reading about aviation and fishing. His room was reportedly filled with books on both subjects.
These interests also proved to be his undoing as the wily Cesare knew just how to exploit them. Carlo would usually fish in a heavily guarded private lake in his father's estate. However the security precautions had neglected the third dimension. One day, while Carlo was fishing from a boat in the lake, Cesare flew in and landed in a small flying boat and invited Carlo on board. Before the security guards around the lake could react, Carlo had climbed in and the aircraft had taken off.
Throughout the time with Cesare, it was likely that Carlo did not know or understand that he had been kidnapped. He probably thought he was being invited on an adventure to travel, see the world and, most of all, fish. Carlo waved to the security guards by the lake. When travelling to England from Canada with Cesare under the assumed name of Cornelli, Carlo would have had ample opportunity to alert the security or customs officials at the airports but did not do so. Subsequently Cesare brought him to a fishing hotel, the Richmond Arms, at Tomintoul in Scotland. For various reasons, one of which might have been that the fishing there was not good, they then went on to fish on Loch Ness. Even later, Cesare brought him to other lodgings on the Spey, near Newtonmore. Carlo's fortunes, both fishing and otherwise, improved when Cesare had to go to London. Left to himself, he met a English gentleman, Major Grey, who invited him to be his guest at Tromie Lodge and to fish at his private stretch of water on the Tromie.
All this time, Eddie Ross, with Biggles and co. were hot on the trial of Cesare and Carlo. Cesare's partners in crime and later enemies The Viper and Mack were also in pursuit in order to settle a score. But Carlo was probably oblivious to all this. At the end of the book, even as the police and the gangsters were converging on Carlo on the banks of the Tromie, Carlo was more preoccupied with his fishing, having just hooked a large salmon. Nor did he notice the gunfight between Cesare and the Viper. By this time he had slipped and fallen into the river after trying to gaff his fish. Swept along by the currents, he was knocked unconscious when he hit some rocks and probably didn't even hear the gunshots. Biggles rescued him and took him to a hospital where his father subsequently joined him.
We are never told how Carlo reacted when he finally learnt the full facts of his adventure. Certainly he did not come to much harm--he would have written off his injuries as a necessary risk in fishing. Biggles called Carlo "a poor rich boy" but one hopes his position improved with the death of his father's enemies.