Coburn is a cynical atheist federal marshal hired by the government to investigate Ivan Isaacs and Temozarela. He first appears to save Lizzie from being hung as a witch after Jarbilong's work on Saint Baldas and subsequently hires her to help him find Isaac. He later appears trying to track down Ivan over a desert and during this Coburn reveals to Lizzie how he knew her father, and how he escaped by jumping off a ravine. During Ivan's battle with Achmode, the group comes across Little Bosack to find it a ruin inhabited only by corpses. Father Lucian stops to pray for the souls, but every corpse suddenly comes alive and attacks them. Coburn shows himself skilled in fighting, using two guns and a whip to destroy the zombies. After escaping, they meet Ivan at the other side of a ravine.
Coburn demands that Ivan give himself up for questioning, and Cairo then shoots at him, against the protests of Father Lucian. However, Ivan responds by jumping into the ravine, while Coburn tries to follow him. However, Father Lucian persuades him not to, just before Lizzie jumps after Ivan.
After Cairo is killed by the Order of St Vertinez, the same group which released Temozarela, Coburn calls in for reinforcements, although his use for them is unknown. After this, they go to Windtale and try to persuade the Mayor that his town is next to be plagued by Temozarela. However, their pleas fall on deaf ears, and Coburn leaves, remarking 'Either way, this town is doomed'. This is later fulfilled as Coburn appears once again after Netraphim just as the village is surrounded by members of St Vertinez. He lights up a cigarette and tells Mr. Dudley that this is personal.
During the battle of Windtale, Coburn remarks on the skill of St. Vertinez and joins in the fray with Lucian and Novic. In the fight he meets up with Joshua and they clash in a duel where Coburn realizes Joshua knows his weakness. He is stabbed just above the heart by Joshua but withdraws the sword and gives it back, telling him to 'aim a bit higher' as he gets ready to fight again.