The Outsider ending explained: Who is the killer?

Stephen King, an American author, is the author of The Outsider (2018), a horror novel. Scribner published the novel that was subsequently adapted for the HBO series. The Outsider begins as a "True Detective"-style murder mystery, created by Richard Price and partially directed by co-star Jason Bateman.

The series concluded with a tense and explosive finale. The question on everyone’s mind is the identity of the killer. In the final confrontation, El Cuco, a supernatural entity, is revealed as the perpetrator. This shape-shifting monster killed Frankie Peterson as Terry Maitland, setting off a series of tragic events.

The Outsider leads a shocking crime to a supernatural mystery on HBO. Frankie Peterson, an 11-year-old boy in a small town, is murdered to start Stephen King's series. Ben Mendelsohn's detective Ralph Anderson thinks he has solved the case by arresting Little League coach Terry Maitland.

However, as the investigation goes on, video evidence supporting Terry's alibi makes it harder to believe that he's guilty. Further, it turns the case into a complicated supernatural puzzle that stays in the minds of the viewers throughout the series.

The official synopsis of the series mentions:

When an insidious supernatural force edges its way into a seemingly straightforward investigation into the gruesome murder of a young boy, it leads a seasoned cop and an unorthodox investigator to question everything they believe in.

As they deep a bit more, Ralph and his team discover a chilling truth: El Cuco, the real killer, can change appearances. This truth is so surprising for the team as well that the murder investigation turns into a fight against a malevolent force that feeds on suffering.

In the finale, Ralph and Holly Gibney track El Cuco to its lair and face it in a cave to end its terror.

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The Outsider ending: The eerie revelation of the killer

The series initially presents a straightforward murder investigation. Ralph Anderson is convinced of Terry Maitland’s guilt, supported by strong forensic evidence.

However, Terry’s claim of being miles away, backed by video footage, forces Ralph to reconsider. This twist propels the narrative into uncharted territory, introducing the supernatural element that defines The Outsider.

Holly Gibney’s discovery

Cynthia Erivo plays private investigator Holly Gibney. Her keen observation skills reveal El Cuco.

In various cultures, this entity can take the form of its victims and commit heinous acts, feeding on the grief and chaos. Holly's revelation shifts the investigation from humans to a supernatural predator.

The Outsider ending: The eerie revelation of the killer (Image via HBO)

The supernatural entity: El Cuco

El Cuco’s modus operandi involves mimicking individuals to commit crimes, creating an almost airtight frame. It targets families, relishing the sorrow it leaves in its wake.

The series builds tension as the investigators piece together the evidence, leading them to the entity’s lair. The struggle against El Cuco becomes a fight for survival, emphasizing the theme of confronting and overcoming unseen, malevolent forces.

The climactic showdown

In the final episodes, Ralph and Holly track El Cuco to a cave, an unstable and dangerous environment.

Despite the risk, they enter, determined to end the entity’s terror. During the confrontation, Claude Bolton, whose identity El Cuco had assumed, unexpectedly appears and delivers a fatal blow to the creature.

Ralph, suspecting the entity might still be alive, ensures its demise by smashing its head with a rock, hoping to end the nightmare once and for all.

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Mid-Credits scene: Lingering doubts

The Outsider ending explained (Image via HBO)

The Outsider concludes with a mid-credits scene that leaves viewers questioning El Cuco’s fate.

Holly, back at her home, experiences a chilling vision of Jack Hoskins, a police officer who had fallen under El Cuco’s control. This encounter suggests that the entity’s influence may persist, planting seeds of doubt and paranoia in Holly’s mind.

The revelation of El Cuco as the killer complicates the story and forces the characters to face an unimaginable evil. The series ends, but the lingering questions and eerie mid-credits scene suggest the supernatural war continues.

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The Outsider is available to stream on HBO.