In Ghost Story, he's a brawny young man, tall and better filled out than the last time Harry Dresden saw him. He had dark and untidy hair, intense grey eyes, and a deep dimple in his chin. Dresden thought Daniel looked like he was sitting on a hot stove and "ready to bounce up at any second, boldly do something ill conceived". William Borden seemed to be focused on Daniel. Daniel scowled at Will, but quickly backed down as though he had "run afoul" of him before.
Daniel seems to be quick to act, and has little patience for subterfuge. He is also impatient as to the disposition of two of the swords, and leaving Sanya vulnerable as the only remaining Knight of the Cross. This led him to spilling the secret in front of one of the White Court.
In the series
In Proven Guilty, Daniel has taken Molly's place as the oldest sibling after she moved out. He "takes a spiritual flogging" after drawing the attention of the fetches away from the rest of the family, so Charity Carpenter can hide them in the safe room. However, despite it, he shows enough presence of mind to climb up into the tree house where Hammerhands can't follow.
In Ghost Story, Daniel Carpenter is a member of the Chicago Alliance and a skilled knife fighter. He also wants to see Amoracchius put to use, and is frustrated that Murphy has not employed them.
He is in attendance at a meeting of the Chicago Alliance at Karrin Murphy's home. When Felicia Raith, a White Court vampire, arrived, he reacts strongly to her allure, likely because of his age, and the inherent hormones of post puberty. During the meeting, in his zeal at wishing to fight the enemy he unwisely let slip that Murphy has possession of two of the Swords of the Cross in front of her. He demanded that Murphy "bring forth the Swords". Murphy asked him to leave and help on watch.
Later, he tried to stop Waldo Butters and Fitz from entering Aristedes' hideout then agreed to help them when he learned that Father Forthill is held prisoner inside. He and Butters pretend to be Wardens while Harry locates Forthill. When Aristedes spots the ruse, he attempts to kill them, but Daniel challenges Aristedes, and he is clearly well-trained, strong, with inherent ability to fight. Aristedes has Kinetomancy-enhanced speed. They are both injured badly but Aristedes retains control, although Daniel holds his own well. This lasts until Fitz comes back to stand up to him and take control of the gang. Fitz orders Forthill freed and EMTs called. Daniel asked him why he came back and Fitz answered that Dresden told him he'd always be running if he didn't come back. Daniel no longer suspects that Harry is some entity pretending to be Dresden.
In Bombshells, Molly Carpenter mentions in passing Daniel's "M9 bayonet[Footnote 1] which he brought home from Afghanistan",[Footnote 2] indicating that at some point he has served in either the U.S. Army[Footnote 3] or Marines[Footnote 4] overseas.
In Peace Talks, Daniel Carpenter has rejoined the military, after recovering from his injuries and avoiding a scrape with the law. Stationed in the Southwest,[Footnote 5] he's married with his first child on the way.