According to chronicles written by Theophylact Simocatta around AD 630, a Byzantine soldier named Bousas was captured by the Avars at the Siege of Appiaria in 586 or 587. The Avar leader threatened to kill Bousas if his ransom were not paid. The citizens were either unwilling or unable to put up the money, allegedly due to the powerful influence of Bousas' wife's adulterous lover. Bousas, embittered by his countrymen's lack of helpfulness, found a way to save his own life, by teaching the Avars to make siege engines and helping them capture the city.
The veracity of the entire anecdote is questionable, and Bousas is not referenced in any other primary source.
Bousas in Thessalonica
The victimization and subsequent defection of Bousas occurred ten or so years before the Avar siege of Thessalonica. Rufus, who told Bousas' story to George, had no idea what happened to Bousas' wife and her lover, but imagined it wasn't pretty.