"Sir Aldingar" is Child Ballad #59.
The title knight tries to seduce the queen. When she rejects him, he puts a leper in her bed and told the king that she was unfaithful — and not even with a right good knight. The king orders them both executed. The queen demands a trial by combat, if she can get a champion. A messenger in search of one is sent back by what looks like a four-year-old boy, but who knows what the queen dreamed. He appears and mortally wounds Aldingar in the fight. Aldingar confesses. The king and queen are reconciled, and the leper is miracluously cured and serves the king as a steward.
Francis Child's variants listed here.
- Beauty = Goodness: The mysterious, possibly angelic champion who fights for the queen.A louelie child was hee;
- Bedmate Reveal: The queen finds herself in bed with the leper.
- Deathbed Confession: Aldingar is mortally wounded by the mysterious champion, and confesses his Malicious Slander before he dies.
- Dreaming of Things to Come: The queen recounts a dream of having been attacked by a grim beast and saved by a little hawk. Now that she has been attacked by Malicious Slander, she sends a messenger to search for a champion.
- Duel to the Death: Aldingar and the mysterious champion's Trial by Combat ends in Aldingar's death.
- Historical Fiction: In some versions, the king and queen are Henry Plantagenet and Eleanor Of Aquitaine.
- Malicious Slander: When the queen rebuffs the titular knight, he puts a leper in her bed and accuses her of adultery to the king.
- Not What It Looks Like: The king finds the queen in bed with the leper, and comes to the wrong conclusion.
- Right Makes Might: The queen's innocence is vindicated by a beautiful little boy who successfully defends her in Trial by Combat against a grown knight.
- Swarm of Rats: In some variants, the queen's hair is unkempt from the mice and rats gnawing on it while in prison.
- Trial by Combat: The queen demands this as her right when defending herself against Malicious Slander.
- Woman Scorned: Gender Flipped. Sir Aldingar slanders the queen with charges of infidelity for having rebuffed his advances.