Harry Potter and the Order of the Phoenix
There are two Theodore Notts in Book 5, and neither of them appears for very long. There is Theodore Nott, Sr., who is a Death Eater who takes part in the ambush at the Department of Mysteries. He gets injured in the proceedings, and Lucius Malfoy shouts, "Leave Nott, leave him, I say – his injuries will be nothing to the Dark Lord compared to losing that prophecy" (35.84).
Then there is Theodore Nott, Jr. He is a son of Theodore Nott, Sr. and a Slytherin. He is a "weedy-looking boy" (26.112) who is clearly furious that Harry has publically named Nott, Sr. as a Death Eater. But, his father is a Death Eater, so his protests seem a little pointless.