In just one week, we will find out who is taking home the iconic Mirrorball trophy for season 21 of "Dancing With The Stars." While Bindi Irwin continues to perform outstanding numbers, impress the judges and receive the highest of scores, the three other remaining male contestants aren't far behind and we officially know who will be headed to the finale.

Monday night's episode was one of the toughest challenges in "DWTS" history for these four couples as they had to perform three dances each, which is something that has never been done before. Because Tamar Braxton took herself out of the competition following last week's show due to illness, nobody was eliminated on Monday night, leaving Irwin, Alek Skarlatos, Carlos PenaVega and Nick Carter all headed to next Monday night's finale. From there, they will each dance a freestyle dance to determine which three couples will become the top three for season 21. On Tuesday Nov. 25, one of these four stars will be crowned the winner, and after last night, it's hard to tell who really is the fan favorite.

Irwin and her partner Derek Hough continue to shine week after week, and she has received the top scores from the judges in almost every single dance, but last night we saw the 17-year-old animal activist in jeopardy for the first time alongside Carter and his partner Sharna Burgess. While it is unclear exactly which of these couples had the lowest scores and truly would have been going home if there was an elimination, host Tom Bergeron did say that one of them had the lowest combination of scores and votes from the previous week. It's hard to imagine that this could be Irwin after her high scores and popularity on the show, but Carter is also a fan favorite and has also been doing well, so we may never know who was at the bottom.

For the first round of dances, which was the individual round, Irwin and Hough opened the show with an energetic and joyful salsa to "You're Never Fully Dressed Without a Smile." While it wasn't absolutely perfect, they did still score a 27 out of 30. Then Skarlatos and his partner Lindsay Arnold danced a beyond beautiful waltz to "America the Beautiful." The waltz was absolutely breathtaking, and even though the judges did still think Skarlatos looked a little stiff, it was the best they had seen him perform yet and they had no choice but to give him his first perfect score of the season. PenaVega and his partner Witney Carson then performed a contemporary dance to "Drag Me Down," which the judges had some mixed feelings about. Bruno Tonioli loved it, while Carrie Ann Inaba and Julianne Hough thought it needed some work. Either way, he still received a high score of 28 out of 30. Carter and Burgess just couldn't get this one right as Carter suffered a few footing mistakes and completely lost it in the middle of his dance. Thank god for Burgess saving him and making sure it didn't completely stop him from going on with the performance. They received a 24 out of 30 for their not-so-perfect tango.

For the dance-off round, it was PenaVega vs. Skarlatos going head-to-head for that extra three points with a cha-cha to "Fun." PenaVega and Carson ended up being out Skarlatos, even though Inaba was really impressed with Skarlatos. Irwin and Carter then went head-to-head with a samba to "Lean On," and Irwin and Hough were the clear winners from the start. Next came the final round, which was the trio round. The remaining four couples were joined by other pro dancers Karina Smirnoff, Mark Ballas, Emma Slater and Peta Murgatroyd, and both Irwin and Carter got well-deserved perfect scores for their three-person dances. PenaVega was not far behind with a 29 out of 30, and Skarlatos received a 27 out of 30 for his not-so-consistent performance.

The totals for the night left both Irwin and PenaVega with 60s, thanks to those extra three dance-off points; Skarlatos with 57; and Carter at the bottom with 54. Irwin has remained at the top for the entire season, and everyone just loves her positive attitude and bright personality, so it would come as quite a shock to most if she didn't win this competition, but you never know what could happen in a competition as challenging as this one.

Watch these four couples compete their hearts out for a spot in the top three on Monday night's episode at 8 p.m. on ABC.