Lost Boy was an Ogron who befriended Sarah Jane Smith. "Lost Boy" was the translation of his name, which members of the Remote pronounced "Frayyt". Ogron names were based on their place in a family structure; Lost Boy (and his older brother, also called Lost Boy) were so named because they were orphans. Lost Boy felt inferior to his older brother, who had darker skin and longer arms than he did.
Lost Boy and his brother were bought by a representative of the Remote, to be used as what they called "hardware". The Remote implanted a universal translator into their heads, and taught them how to use computers. Guest used Lost Boy and another Ogron as security at COPEX in 1996, reasoning that the human attendees would think that the Ogrons were merely ugly foreigners.
When Lost Boy saw the weapon buyers at COPEX, he recognised that they were the same as the slavers who bought Ogrons, and he decided that there was no reason for him to obey the Remote just because they had bought him. He sought out Sarah Jane Smith, who had escaped from the Remote, and offered his services. Using the receiver Lost Boy had taken from the Remote, K9 Mark III was able to translate his speech with more precision, as the receiver could pick up the subsonic frequencies which were part of Ogron language, and usually lost in Ogron communications with non-Ogrons.
Lost Boy accompanied Sarah Jane in her efforts to find the Doctor's TARDIS and rescue the Eighth Doctor from Saudi Arabia, where he was being tortured. After the Doctor was rescued, Lost Boy remained on board his TARDIS when Kode took it to Anathema. There, the Doctor and Samantha Jones prevented Guest from detonating the Cold, and transported Anathema to a new location. Lost Boy decided to stay on Anathema because "here, nobody cares how long my arms are." (PROSE: Interference - Book One, Interference - Book Two)