Colonel Douglas Mortimer is an efficient Bounty hunter who roamed the Western frontier. He makes his appearance in the Film: For a Few Dollars more. During the events of the film he is first seen pursuing an outlaw for the price upon that individual's head. He then picks up the trail of notorious villain El Indio after discovering a Bounty on the Villain's head. After traveling to the town of El Paso he briefly encounters several members of El Indio's gang in a local Saloon; he deliberately insults one of the men, however, rather than retaliating,the gang members leave after the initial confrontation. As night settles over the town he encounters The Man with no Name after witnessing his presence several times during the day. After the two prove their efficiency with a weapon they discover that they are both looking for the same Outlaw and the two form an uneasy alliance.
They soon create a plan to allow The Man with no Name to infiltrate the gang while the Colonel works from outside the group, The Man with no Name fulfills a significant portion of his role in the plan before the alliance between him and the Colonel is almost untied, after a brief argument the two decide to continue working together and they agree to lead the rest of El Indio's gang to the Rio Bravo Canyon. The Man with no Name breaks the agreement secretly as he wishes to defeat the gang alone. The Gang decide to head East to a small Settlement known as Agua Caliente which lies in a mountainous region. Colonel Mortimer predicts the move however and purues them to the area.
The Colonel confronts the gang in a local Saloon were he meets several of the gang members that had met him in El Paso and the gang member known only as Hunchback. The Hunchback challenges the Colonel to a duel, the Colonel kills him withe ease, and he tells El Indio that he wishes to help them open the safe that the gang had stolen in El Paso, but he wants five thousand dollars in return. After the safe is opened El Indio reveals that he wishes to lock the safe away until the law has given up on pursuit. The Man with no Name and the Colonel agree that they should steal the money from the safe. Their plan is uncovered by the gang and the two are captured and brutally beaten for the gang's enjoyment. The two are released soon afterwards due to another plan by El Indio, but the plan heads slightly southwards for El Indio and the two Bounty hunters soon return, they clean the streets of Agua Caliente building by building and soon enough Colonel Mortimer confronts El Indio in a final Standoff. Mortimer claims victory as he shoots El Indio down. It is revealed that he had pursued El Indio not for the bounty, but because El Indio savagely raped Mortimer's sister years before, an act which caused her to claim her own life.
After refusing his share of the bounty and bidding farewell to The Man with no Name, Mortimer mounts his horse and rides away from Agua Caliente and into the Desert. It is unknown what happens to him after the events of the film.
Lee Van Cleef also played the part of Angel Eyes in The Good, the Bad and the Ugly. Angel Eyes bears many similarities to Mortimer.