Thiago is a young Mexican American man living in Chicago, struggling with profound and disorienting grief following the sudden death of his wife, Vera. A former college dropout who previously worked odd jobs to care for his sick father, he recently inherited a substantial life insurance payout. He harbors a deep distrust of others due to his traumatic upbringing and prefers isolation over socializing. His sorrow leaves him vulnerable to strange occurrences inside his home.

Vera is Thiago's late wife, an intelligent and pragmatic woman who passes away after a tragic fall at a Chicago train station. Before her death, she worked and lived with Thiago in a condo plagued by strange phenomena, where she eagerly adopted a new smart speaker called an Itza. Though physically absent, she remains a constant presence in the narrative through Thiago's memories and his ongoing internal dialogue with her.

Diane is Vera's tough, resilient mother, originally from Mexico. She holds strong Catholic beliefs and initially disapproved of Thiago, viewing him as a burnout before he married her daughter. Bound to Thiago by their shared sorrow, she attempts to manage her profound loss while maintaining a pragmatic, superstitious approach to the supernatural elements surrounding her daughter's old apartment.

The Cook is an unsettling, gaunt man with protruding eyes who operates a quiet diner far from the main interstate. He serves Thiago a free milkshake while discussing suffering, presenting disturbing philosophical theories about forces that persecute humans to trick them into surrendering their bodies. His sudden appearance far from civilization sets an ominous tone for Thiago's journey.

The Entity is a formless, menacing presence that initially seems to inhabit the couple's "Itza" smart speaker. It communicates using eerily context-appropriate movie quotes and creates an atmosphere of intense dread in the home. It feeds on negative emotions, actively preying on Thiago in his vulnerable state of mourning.

Esteban is an undocumented youth whose attempt to flee after stealing a phone results in the tragic accident that claims Vera's life. His lack of identification papers turns the accident into a political talking point. He insists he only looked back on the platform because he heard someone call his name, adding an element of mystery to the tragedy.

Fidelia is the former tenant of the Alvarezes' Chicago condo, an older Spanish-speaking woman who was evicted before they moved in. Before leaving, she allegedly left behind an animal carcass, candles, and a large door shape drawn in blood on the wall, leaving a lingering mystery for the new owners.

Brimley is a friendly, energetic St. Bernard dog that Thiago adopts in Colorado to help stave off his overwhelming loneliness. The dog provides a temporary sense of comfort and companionship in the isolated cabin, though his presence also reminds Thiago of the life Vera will never experience.

Dr. Jacobson is a local Colorado veterinarian whom Thiago consults regarding the stray St. Bernard he eventually takes home. He acts as a grounded, scientific voice when Thiago attempts to understand the hazards of the rural landscape, suggesting logical explanations for the dangers in the woods.

Raul is Thiago's abusive, alcoholic father who left a lasting psychological mark on his son. He moved back in with Thiago and his mother after being kicked out by his wife following an affair. He passed away after Thiago dropped out of college to help care for him.

Mr. Diaz is Vera's stepfather and Diane's husband. He maintains a distinct distance from Thiago, sharing his wife's initial skepticism about their son-in-law and prioritizing his own immediate family's well-being over Thiago's inclusion.