Dumont Boyle is a major antagonist in the book Eagle Day by Robert Muchamore. He is a sixteen year-old French boy who befriends a group of children trying to escape from occupied France with British agent Charles Henderson, only to prove himself to be selfish and malevolent.
Dumont is a stereotypical teenager, as in he does stupid things to impress his friends, such as urinating in Major Ghunsonn's car and drinking wine, even though it makes him sick. He is also desperate for respect within his friend circle and threatens them, especially Paul Clarke, if he perceives that he is being disrespected, as well as claiming that he has broken into almost every house in the area. He is also demonstrated multiple times to be stupid, such as when he doesn't understand a simple joke in a propaganda leaflet and admits to not being able to read. He is eventually demonstrated to also be extremally lustful, when he corners Paul's sister Rosie and makes inappropriate comments about her and touches her in an extremally perverted way.
Dumont is first introduced as the sixteen year-old son of wealthy French farmers Luc and Vivien Boyle. He appears first in Chapter Thirteen when his young cousin Lucien roughhouses with him after arriving at Luc's house. He immediately makes friends with child agents Marc Kilgour and PT Bivott, who he competes with to see which one of them can drink the most alcohol without being sick. It is mentioned that he succeeded in out-drinking Marc, although the wine upsets his stomach. He later showed them how to hunt and skin rabbits in order to eat them.
In Chapter Fifteen, Dumont is seen out hunting and burgling with Marc and PT. Because they are in a military zone, many of the farms are abandoned. Dumont claims to have broken in to them and stolen many valuables that the owners left behind. However, he is lying, and when he takes PT and Marc into one of the houses, it only contains tools and pots. When they get bored of burgling, they throw rocks through the windows of some of the houses. Marc and PT say they should go home, upon which Dumont calls them "mummy's boys", before getting distracted by an open-topped German car. He bets PT ten American dollars that he'll go over to the car and urinate in it. PT refuses, saying he doesn't want the Germans to kill Dumont, but Dumont does it anyway, before running into the trees and escaping.
After the RAF drop mocking leaflets on the town while a member of the Nazi Party is inspecting a nearby operation, Dumont, Marc and PT meet up with Paul Clarke, friend of Marc and PT, to read one of the leaflets. Dumont gets into an argument with Paul over his intelligence, during which Dumont threatens Paul with violence, only to be distracted by Marc. Dumont then suggests burgling a house which he claims belonged to a rich family, to which Marc invites Paul. When they arrive at the house, Marc sees that the grass has been freshly mowed and denies that the house is empty. However, Dumont disproves this by saying that the lawn was mowed by the caretaker, who has burst his appendix. PT then breaks into the house and Dumont immediately breaks two china ornaments. He reveals that the house is owned by Mr LeConte, a man who bought the house with money he stole from Dumont's grandfather, and he broke in to get revenge. After it is revealed that he can't read, Dumont becomes enraged and threatens to murder Paul after the latter offered to teach him. After Paul goes home with a pile of books he stole from LeConte's house, Dumont is sick after drinking stolen wine from LeConte's kitchen. Before they can get home, the three of them are accosted by German soldiers, who arrest them for peeing in their car.
Dumont and the others are taken to a prison in Calais for sabotage of German property, where they are imprisoned in a filthy cell and Dumont has a noose tied around his neck, with a soldier saying that they are waiting to find a tree from which to hang him. Major Ghunsonn, the owner of the car, enters the cell and threatens to shoot Dumont without trial, calling him a spy and a cockroach. Marc says that Dumont's family could pay damages, prompting Ghunsonn to slap him for attempting to bribe him. However, British agent Charles Henderson, who is posing as Marc and PT's father, is able to get them released, although Dumont is beaten badly.
When Henderson and the others are preparing to blow up the harbour and leave for Britain, Dumont sneaks into their house and noses around in the bedrooms. Paul's thirteen year-old sister Rosie comes across him and informs him that Marc and PT have gone out. Dumont says that Rosie is pretty and comments that he wants to be her boyfriend. When Rosie tells him to "go home and take a bath", Dumont hisses with rage and pins her against a wall before sexually assaulting her. She pretends to submit, telling him how powerful he is, before biting him when he tries to kiss her again. She then beats him with a frying pan to subdue him and locks him in Henderson's bedroom. When Henderson arrives home, Rosie tells him that Dumont tried to rape her. He confronts Dumont and threatens to kill him with a cleaver. Dumont begs for his life, calling Rosie a "lying b***h and claiming she attacked him first, however this only makes Henderson angrier. Rosie begs for him to spare Dumont, prompting him to knock Dumont out and tie him up in the barn, along with Luc when he tries to find Dumont.