On the latest installment of crime series "Castle," three people came forward to confess to one murder.

In "Room 147," the murder victim is Justin Marquette, a struggling actor who is found fatally shot in room 147 of a Best Traveler's Hotel.

Justin's off-Brodaway theatre company tells Castle (Nathan Fillion) that Justin was threatened by a woman named Anita a few days before. Anita then confesses to the murder, describing the murder in detail.

Yet, the story doesn't end there. It's discovered that Anita has a solid alibi for the time of the murder. But she still sincerely believes she murdered him.

Then a man named Sam also confesses to the murder, and gives the same details as Anita. And, like Anita, he says he never met Justin and doesn't know why he killed him. Both suspects also do not remember the last two weeks.

While Sam and Anita are arguing over who really killed him, another person confesses to Justin's murder. The man, who is named Dwight, confesses, but no one wants to hear it, as they already have their hands full with the other two puzzling confessions.

But when Dwight confesses, the team notices that there is a symbol drawn on his hand, and it was the same symbol seen scribbled on Anita's confession—a triquetra Wiccan symbol.

The symbol makes the team believe that the three suspects are connected, even though they claim not to know one another. It's then discovered that a red van was parked outside each of the confessors' houses two weeks ago.

They trace the vehicle to EHI, a cult that uses a triquetra as its symbol. The cult's leader is Dr. Bower, a man who claims to have a PhD, and preaches strange philosophies. Castle and Beckett (Stana Katic) go to visit Dr. Bower, but have to video chat with him because he's apparently in Stockholm. He is very uncooperative, and denies being connected to any of it.

Drug testing reveals that all three confessors have been drugged with memory-inhibinting substances for the past two weeks.

Castle and Beckett figure out the three confessors' details of the scene of the crime are not correct. They also find out that EHI rented a floor of a different hotel within the same chain for an event two weeks before.

Security footage then shows Bower meeting with Justin in the lobby, which gives the team enough evidence to get a warrant for Dr. Bower.

They find out that he's not in Stockholm—he's actually in the EHI building, shredding files that could incriminate him. He admits that he hired Justin to do an experimental therapy film. The participants in the film were given drugs and shown the film of Justin being killed (a simulation of his murder) in the hopes that they would project their demons onto the murder, and experience "murdering their problems."

The participants then began to think that they actually committed murder. To erase the negative effects of the experiment, Dr. Bower drugged the confessors so they would forget their involvement in EHI.

Bower is therefore not a murderer. It turns out it was Pam, the stage manager in Justin's theater group. She killed Justin because she hates EHI because her brother died in an incident for which EHI was responsible. Therefore, she killed Justin to implicate EHI for a crime that would bring down the organization.

Meanwhile, in the episode, Alexis (Molly Quinn) is reluctant to move back into Castle's place after breaking up with her boyfriend, but eventually decides to move back in.

On the next episode, "In the Belly of the Beast," Beckett will get involved in an undercover investigation.

The synopsis reads: "When Beckett helps out on an undercover Narcotics investigation, the mission turns deadly. To survive, Beckett is forced to use her wits with some of New York's dangerous underworld and a powerful enemy from her past."

Also, it has been confirmed that "Castle" will have 23 episodes this season.

Check out the promo below for "In the Belly of the Beast," which airs Monday, March 3 at 10 p.m. EST on ABC.