Eddie makes his debut in The Drawing of the Three, in which Roland encounters three doors that open into the New York City of our world in different times. Through these doors, Roland draws companions who will join him on his quest, as the Man In Black foretold. The first to be drawn is Eddie Dean, a drug addict and a first-time cocaine transporter. Eddie lived with his older brother and fellow junkie Henry, whom Eddie reveres despite the corrupting influence Henry had upon his life. Roland helps Eddie fight off a gang of mobsters for whom he was transporting the cocaine, but not before Eddie discovers that Henry has died from an overdose of heroin in the company of the aforementioned mobsters (after which the mobsters decide to chop off Henry's head). It is because of Eddie's heroin addiction that he is termed 'The Prisoner', and that is what is written upon the door from which Roland draws him.

Roland also acquires medicine for his infection during the trip to Eddie's world, but this only temporarily quells the fever.

Eddie passes through the door into Roland's world, and faces heroin withdrawal symptoms, but despite his suffering, he also shows an affinity for the ways of the gunslinger. Unwillingly at first, and somewhat under duress, Eddie becomes Roland's companion through Mid-World, and he soon falls in love with and marries Susannah, the next member of Roland's ka-tet.

In the final novel, during the attack on Algul Siento, Eddie is shot and killed by Pimli Prentiss, the master of the establishment.

Roland also notes that Eddie's character strongly resembles that of Cuthbert, a gunslinger of Roland's past, and one of Roland's greatest friends. The character of Cuthbert is mentioned in Browning's poem and is described most fully in Wizard and Glass, although he is first mentioned in The Gunslinger.