'Dancing With the Stars' sees its final 4 couples in a close race to the finals

LOS ANGELES -- The "Dancing With the Stars" semi-final round is packed to the rim with dancing. Four couples are doing three routines a piece: one style they've not yet danced, a trio dance with a fellow pro and a dance-off challenge.

The dance-off pits Bindi vs. Nick, and Carlos vs. Alek. The winner gets three points added to his or her score. The non-winner (I had to say loser!) gets zip. Let's get started with this week's math challenge. I'll list the score for each routine, with recaps from highest to lowest.

BINDI IRWIN - 60 points total

First dance: Salsa - 27 out of 30

Bindi and Derek dance to Sia's funky version of "You're Never Fully Dressed without a Smile," and they manage to make the Salsa fun and uplifting. It ends with confetti falling from the ceiling and Bindi declared "It's raining happiness!" The judges all agreed that the routine was very good, but they wanted a little more of the "down and dirty" true Salsa hip action.

Second dance: Samba dance-off - 3 points

Third dance: Jazz trio with Mark Ballas - 30 out of 30

Derek and Mark have a shorthand with one another that's pretty funny to watch. Bindi just sits back and waits until it's her turn to learn, and then she does it with a vengeance. There's some risky moves in the routine, but they know this is the time to just go for it. The judges loved everything about it (hence the perfect score). From the choreography to the staging to the lighting - the routine highlighted the best of Bindi.

CARLOS PENAVEGA - 60 points total

First dance: Contemporary - 28 out of 30

Carlos and Witney get to do a Contemporary, which suits his muscular build just fine. There's a rope, and he does some tricks that might defy gravity a bit. Bruno Tonioli called the dance "bloody good" and gave them a 10. The female judges liked it, but felt something was missing. They couldn't quite put their fingers on what, but something.

Second dance: Cha Cha dance-off- 3 points

Third dance: Charleston trio with Karina Smirnoff - 29 out of 30

Carlos has a bit of a scare when both pros tell him they've never done the Charleston on the show before. But that's what the internet is for, right? Obviously there was a lot of research done, and some daredevil moves in rehearsal, and it all came together. Carrie Ann called the dance so much fun, and said she couldn't take her eyes off Carlos. Bruno said he stole the show from the women. Julianne agreed and said it was Carlos who looked like the professional.

ALEK SKARLATOS - 57 out of 30 total

First dance: Waltz - 30 out of 30

Alek and Lindsay danced a fluid Waltz to "America, the Beautiful" and the choreography really highlighted how far Alek has come in these 10 weeks of competition. Carrie Ann called it his best performance to date, and Julianne thought he brought technique, character and the whole package to the ballroom.

Second dance: Cha Cha dance-off - 0 points

Third dance: Argentine Tango trio with Emma Slater - 27 out of 30

Alek can't hide his boyish grin when he mentions Emma's name and it's adorable. This dance has to be fierce and sexy, and he has to match the girls in power. And he does. Bruno thought he handled the double dancers like an expert. Carrie Ann was impressed with his frame and strength, and Julianne called the dance powerful.

NICK CARTER - 54 points total

First dance: Tango - 24 out of 30

Nick and Sharna attack the Tango, maybe a little too vigorously. A minor mistake looks like it could mess them up, but she gives him a pep talk mid-dance and they are back on track. Still, that little boo-boo cost them points. The judges praised their chemistry and commitment, but had to ding them on a mistake.

Second dance: Samba dance-off - 0 points

Third dance: Salsa trio with Peta Murgatroyd-

Sharna's BFF Peta returns to the ballroom after nursing an injury all season. Nick says he gets an "Aussie sandwich." Peta confesses that, like Sharna, she too had a poster (or two or three) of Nick on her bedroom wall when she was a teen. They've got to shake and sex-up their Salsa as much as possible, and Nick is given the marching orders to "move it, move it" during rehearsal. Come showtime, he sure does. Carrie Ann thought it was his most solid dance to date. Bruno liked that they threw in lots of different music moves, but the dance was always a Salsa, and Julianne told Nick everything he has to bring to the table was in this routine.

SPOILER ALERT

It's not even worth trying to psych anyone out. With Tamar's withdrawal, we're already down a dancer, so everyone makes it through to the finals next week!