Big Brother season 27 debuted on July 10, 2025, with 16 players checking into the Hotel Mystère to compete against each other for a $750,000 cash prize and the winner's title. CBS had previously teased the entry of a mystery houseguest, who, according to host Julie, was "very polarizing." As the episode progressed, the mystery person was revealed to be Rachel Reilly, the winner of season 13.
Rachel had recently appeared on The Traitors and was rumored to be in sequester by her friend and Big Brother alum Janelle Pierzina. However, the speculations surrounding Rachel's entry in the latest season of the CBS show turned out to be true. The houseguests were shocked to see the fan-favorite star join them as a player, 14 years after claiming her victory.
However, Rachel joined the cast as the 16th houseguest, not the 17th. That was because the Mastermind, a masked man introduced as the main antagonist in the premiere episode, revealed that one of the existing players was a secret accomplice.
What happened when Rachel Reilly entered the Big Brother season 27 house?
When CBS announced that Big Brother season 27 would have a "summer of mystery" theme, the network also mentioned that a "mystery houseguest" would join as a participant. Throughout the past week, the show had shared cryptic messages and hints on their official Instagram profile regarding the identity of the secret player.
Finally, Rachel Reilly was unveiled as the mystery houseguest during the premiere of Big Brother. She was added to the season by the Mastermind, a person labeled as the villain of the season. The Mastermind shared a video message with the cast members, in which he shared that he would be adding something of his choice to the show.
With that said, Rachel appeared, walking out from behind a fake door. She stood on the staircase, posing in a red dress, surprising her co-stars.
"Floaters, grab a life vest! Reality royalty has officially arrived," she said.
The Big Brother alum descended the stairs, while the contestants witnessing her arrival remained starstruck. They soon began chanting "Rachel!" to welcome the champion into the season 27 house. However, not everyone was pleased with her addition to the show.
In separate confessionals, they expressed their concerns regarding competing against a former winner and someone familiar with the game. College sports podcaster Cliffton "Will" Willis said:
"Are you serious, Big Brother? That’s what we’re doing? Rachel won this show. She’s one of the best to ever do it."
Rachel first appeared on the CBS show in season 12, where she met her future husband, Brendon Villegas. She quickly sparked outrage among the contestants and was eliminated in ninth place. However, she returned in season 13, alongside Brendon and four other returning contestants, determined to redeem herself.
Rachel overcame the competition and made it to the finale, where she earned the winner's title and the $500,000 cash prize. The Big Brother alum then competed in three seasons of The Amazing Race and one of The Traitors.
After Rachel settled in the house, the Mastermind revealed that she was the 16th houseguest, not the 17th, because among the players was a saboteur-like accomplice. This particular person had joined forces with the Mastermind and was tasked with jeopardizing the game of other contestants.
It was up to the houseguests to investigate and figure out the identity of the secret accomplice. However, if they failed to identify it correctly, the saboteur would join the group. With stakes so high, the contestants became suspicious of one another, as they started analyzing everyone and everything they saw.
Big Brother season 27 can be streamed on Paramount+.