Mark won the Head of Household competition after his ally, Big Time Rush singer, threw it to him.
At the subsequent Nomination Ceremony, Mark nominated Brandi, a former The Real Housewives of Beverly Hills star, and Ariadna, Miss Universe 2015, because they were close friends and a power couple in the house.
"It's time to break up this dynamic duo," Mark said in the Diary Room after revealing his decision, adding that Brandi is his target going forward and Ariadna just became guilty by association.
The Celebrity Big Brother broadcast began on Day 20, with former The Apprentice contestant and White House staffer Omarosa Manigault admitting she was "a floater" in the game because her only remaining ally, former NBA player Metta World Peace, asked to leave the house.
Prior to Metta's exit, entertainment reporter and star of RuPaul's Drag Race, Ross Mathews, had convinced actress Marissa Jaret Winokur to work with Mark and James in order to save him (prior to the Power of Veto competition) even though it meant leaving her allies, Brandi and Ariadna, in the dark.
Marissa, James, Mark and Ross came up with a Final 4 alliance called "Roomie Squad," but Marissa's loyalty still lied with her original Final 4 consisting of Ross, Brandi and Ariadna. Marissa wants a woman to win this game; she therefore joined the guys' alliance simply to save Ross.
Although Omarosa was an obvious target and threat in the house at this point, James thought it was more important to break up a pair like Brandi and Ari instead of taking out Omarosa, who was by herself in this game.
Ross, however, thought Omarosa was after him, so he wanted to unite both sides of the house with one common goal -- evicting Omarosa. Marissa was on the same page because she wanted to see Omarosa get the boot instead of one of her girls.
Omarosa also attempted to get inside Marissa's head about how they guys weren't loyal to her after all. But Omarosa's lies were adding up, and the houseguests were starting to think that everything that came out of her mouth was "fake news."
Meanwhile, Ari and Brandi determined their biggest threat was James.
It then became time for the Head of Household competition dubbed "Red Carpet Ride."
The women competed against the women, and the men competed against the men in two heats of competition. They were required to walk or crawl their way across a red carpet that twisted and turned side to side, constantly knocking them off into a pit.
The three players to cross the red carpet in the fastest time without touching the ground would move on to the final heat, and those houseguests ended up being Mark, James and Brandi.
James fully trusted Mark and wanted him to win so that he could play in the next HoH competition. Omarosa realized right then and there that Mark and James had already made a Final 2 deal.
When Mark won HoH, he was excited to step up for his team. He immediately knew he wanted to break up Brandi and Ariadna, but that Omarosa would be a good backup option as well. Marissa and Ross felt safe with Mark in power.
Marissa then campaigned for the target to be put on Omarosa's back instead because the famous reality TV villain was clearly dangerous, but she was unsuccessful.
At the Nomination Ceremony, Mark announced he had nominated Brandi for eviction because she's "athletic, competitive and strategic." Mark also said he had heard through the grapevine she was "lobbying for weeks" to put him up on the chopping block.
Mark then told Ariadna that she shares the same positive traits as Brandi, however, she chose to team up with Brandi -- and that was her mistake and her demise.
Brandi knew James was the one who really orchestrated this plan -- not Mark -- and she called the young singer a "D-bag."
Brandi insisted in the Diary Room that she wasn't about to go down without a fight, and then James was shown calling the former The Real Housewives star "obnoxious." James couldn't wait to see Brandi go next.