They say a chain is only as strong as its weakest link, and though new “Challenge” competitor Rianna has shown some heart, it’s clear she’s starting to corrode.

On tonight’s new “Bloodlines” episode, the game’s final 10 players, who shifted back into their original family-oriented pairs, got a taste of this season’s final challenge through “Wait For Me,” a slog up a mountain punctuated by a series of checkpoints. Oh, and to make the trudge even more fun, each team had to trade off carrying a huge, weighted bag.

As early as the mission’s first ascent, Aneesa and Rianna shocked everyone by taking a commanding lead. More surprisingly, they maintained first place through more than half of the journey and held hands as they powered through the pain.

“It feels good passing everyone,” Aneesa said. “We have a really good chance of winning…we have a great lead. This may oddly be our challenge to win.”

Still, Johnny was convinced the team’s success was exclusively to Aneesa’s credit and predicted Rianna would eventually fall apart.

“This is quite a shock that Aneesa and Rianna made it this far, this fast,” Bananas said. “I think the only thing that saved them was the fact that this long leg they had to do -- Aneesa was carrying [the bag]. I think if Rianna had to do it, she’d still be trying right now.”

And the game’s reliable prophet turned out to be right -- when Aneesa and Rianna reached a basic monkey-bars checkpoint, Rianna absolutely fell apart, and she and Aneesa were forced to watch three teams pass by.

Thanks to the mercy of a 15-minute time cap, though, Rianna and Aneesa were allowed to advance to a final puzzle, where they edged out Cara Maria and Jamie by the skin of their teeth to claim a fourth-place finish. Though they successfully avoided The Pit in the process, Aneesa was suddenly terrified by the day’s implications.

“I’m happy that Rianna pulled it together,” she said. “But I think when it comes to challenges, we’re just at our wits’ end with each other.”

What do you think -- will Aneesa, one of the game’s more solid players, be able to lift Rianna up, and does the duo have a chance at the big prize? Or has Rianna proven she’s too big a liability for which to compensate, and will her limits kill her team’s chances of winning? Tell us what you think, and be sure to see what happens on the next “Bloodlines” episode next Wednesday at 10/9c!