He is introduced to Major Sharpe and his wife Jane, taking dinner with them while Rifleman Harris plays at manservant. When he misquotes Shakespeare at dinner, Harris points it out to Sharpe, saying the man didn't know his literature, but did know women.
While Sharpe was away on a mission, Harris, who was confined to camp, remains in Sharpe's billet, playing the servant, and keeping an eye on things.
Shellington accompanies Sharpe until he sees his first dead men, he then fainted and Sharpe sent him back to camp with two of Colonel Brand's men, saying Shellington would want to go back, and might even try to seduce his wife.
Shellington tries to romance and seduce Jane, playing the romantic, saying such things as bread and water were sufficient in her company to sustain him, that he would see her all night in his dreams, and claimed to have written her a poem. Harris, however, began reciting the poem along with Shellington, and then provided it's provenance and possible author.
Shellington tried to tell Jane that all poets shared the fruits of the same tree, but she slapped him and threw him out - Harris providing a final boot to his backside.
His sketches of Colonel Brand wearing the ring of a murdered gypsy were confiscated by Sharpe and used as evidence in Brand's court-martial.