Detective Estevez is a character in the television series Dirk Gently's Holistic Detective Agency.
Patrick Spring's Murder
As a missing person's detective in the Seattle Police Department, Estevez and his partner Zimmerfield are put on a case to solve the disappearance of Lydia Spring. Believing the case to be died to the subsequent murder of Patrick Spring, the two begin investigating both cases.
Two Missing Bodies
While viewing the body of Patrick Spring, Estevez and Zimmerfield discover that the two other bodies from the crime scene have been taken. A worker claims that they were taken by the FBI but the FBI deny any involvement.
Questioning Todd Brotzman
While walking to work, Estevez comes upon a corgi standing patiently outside the police station and recognizes it from the hotel tapes on the day of Patrick Spring's murder. Believing this to be an important clue, he and Zimmerfield keep the dog secretly in the station while they question Todd Brotzman on his involvement in their cases. 
While unknowingly holding Lydia Spring (in Rapunzel's body) in a box in their office, Estevez and Zimmerfield are approached by Agent Weedle who is now being inhabited by a member of the Men of the Machine. Weedle demands to know why the police haven't brought in Todd Brotzman but Estevez and Zimmerfield are more puzzled as to why Weedle is acting strangely. Weedle leaves but not before letting it slip that he wants to know what happened to the corgi. This leads Estevez and Zimmerfield to agree to keep Lydia secretly in their possession until they know the details of the FBI's involvement. 
Upon further investigation, Estevez and Zimmerfield discover that Gordon Rimmer, who already has several ties to the case, has access to an abandoned Animal Transfer Unit. They ask the police captain, Edmund Doyle, for a warrant to search the warehouse but are ultimately denied, despite their pile of evidence. As a result, Estevez and Zimmerfield go on an unauthorized mission into the warehouse and discover several dead bodies inside. Before they can call it in, Zimmerfield is shot by an electric crossbow and dies in the car when Estevez attempts to drive him to a hospital, leaving Estevez devastated. 
Experiencing extreme emotional turmoil due to his partners death, Estevez goes to the Edmund Doyle and demands that they go back to the Animal Transfer Unit to make some arrests and avenge Zimmerfield. Doyle says that they can't pursue any actions as the mission was unauthorized. Piecing together Doyle's unwillingness to do anything to aid his case, Estevez declares that Doyle is working with the Men of the Machine, an action that results in his disbarment from the police force.
While day drinking in a park, he uses the corgi to uncover the fact that the corgi is actually Lydia Spring, along with the fact that she was soulswapped by Rimmer and taken from Rimmer's house by Dirk and Todd. Determined to solve the case, Estevez barges into Todd Brotzman's apartment and demands answers. While questioning Todd, Estevez begins to hear thumping noises coming from the bathroom and discovers Amanda Brotzman on the ground suffering from a Pararibulitis attack. He carries Amanda out of the building to where the Rowdy 3 can save her. 
Helping Dirk, Todd, and Farah
Knowing that Rimmer was the one responsible for switching Rapunzel and Lydia in the first place, Estevez returns to the Animal Transfer Unit and ambushes Rimmer behind the building. His attack is cut short, however, when Rapunzel (in Lydia's body) comes to her owners aid, distracting him long enough for Rimmer to run off. 
Estevez chases Rimmer through the Transfer Unit, firing several shots that accidentally hit the Soul Exchanger, rendering the machine unusable. Finding Dirk, Todd, and Farah inside the warehouse, Estevez has them locked up but is eventually convinced of their innocence. The four of them take Rapunzel and Lydia to the Spring Mansion to use another version of the Soul Exchanger machine to switch them back. As the Men of the Machine converge upon the mansion, Estevez and Farah are able to team up and take out Gordon Rimmer at last. Following the battle, Estevez takes Dirk to the hospital to recover from his wounds.
Sometime later, Estevez entered the Seattle Police Department but found it was being searched. Initially assuming that Doyle had ordered a coverup, he found the latter shot dead on the floor outside his office. Hugo Friedkin exited the office and shot Estevez on impulse. Friedkin explained that as the new head of Project Blackwing he was conducting a coverup on and purge of the Men of the Machine and anything and anyone connected to the Spring case. Estevez tried feigning ignorance and reached for his gun to defend himself, but was shot twice more by Friedkin, presumably killing him.