Star accepts her ex-boyfriend Tom's invitation to Demon Prom, but Marco is suspicious of Tom's intentions and crashes the prom to prevent Star from getting her heart broken again.
At Echo Creek Academy, a black carriage pulled by a skeleton horse appears from underground in a burst of fire. A demon known as Tom steps out of the carriage and makes his way to the school, passing many girls who just gaze at him. He enters Star's classroom, and after moving a student aside he approaches her and invites her to the Blood Moon Ball. Star immediately refuses his invitation and drags him back to his carriage, reminding him they broke up. Tom tries to convince her that he is now a changed man by showing his life coach, Brian, his bet bunny and a badge which says he's been anger free for fifty-three days. Star is cautiously impressed but just before she is convince, Marco appears from nowhere and karate chops Tom's hand off. This causes Tom to burn with rage, but manages to calm down after his life coach helps him walk it out. Tom again assures her he has changed and before leaving, he gives her a tiny black bell in case she changes her mind about going.
That evening, Star has decided to go to the Blood Moon Ball with Tom. Marco on the other hand is unsure about Star's decision and expresses great distrust for Tom. He offers to accompany her to the ball, but Star tells him to trust her to look out for herself. After changing into her ball gown, she rings Tom's bell, summoning a demonic elevator to take her to the ball. Despite more of Marco's misgivings, Star bids him goodbye and heads down to the underworld. Star soon arrives and meets up with Tom, who was making final preparations to make sure the ball meets her approval. Meanwhile, back home, Marco is sitting in Star's bedroom alone, eating nachos and listening to Mexican music. Just then, he hears a strange voice speaking to him from nowhere, saying there's a "blood moon tonight" and that it's "the moon of lovers". As Marco wonders where the voice is coming from, he spots the black bell on Star's dresser.
Back at the Blood Moon Ball, Star is not having much fun and finds out from a few underworld denizens that Tom made the ball boring just to impress her. Just then the organizer of the Blood Moon Ball announces the start of the blood moon dance; when the light of the blood moon shines through the crescent-shaped skylight, it will select two people and "bind their souls together for eternity". Wearing a skull mask for disguise, Marco approaches Star as the blood moon's light shines down on them. The two of them briefly waltz together before Marco reveals himself under the mask. Then before telling Star they should go home, a furious Tom shoves Marco to the floor as the skylight closes. Angry that Marco stole his dance with Star, Tom is about to burn him to a crisp, but Star freezes him in a block of ice.
Upon returning home, Star yells at Marco for not trusting her to take care of herself. She still understands that he was only trying to look out for her, but tells Marco he has to let her figure things out for herself. On top of that, Star would rather have a friend than a hero. Marco sits beside Star and apologizes for ruining her night, but despite everything else, Star admits she enjoyed their dance together. Then after a few seconds of mysteriously saying the same thing and sharing a laugh, Star commands Marco to make her some nachos.
- Eden Sher as Star Butterfly
- Adam McArthur as Marco Diaz
- Rider Strong as Tom Lucitor
- Stephen Root as Brian
- Jon Heder as Oskar Greason
- In at least one instance when Disney XD aired this episode, the lines spoken by the mysterious voice that Marco hears in Star's bedroom are removed from the episode entirely, making Marco's reaction to them confusing for anyone watching.
- This episode was nominated at the 43rd Annual Annie Awards for "Best Animated Television/Broadcast Production for Children", but lost to the Wander Over Yonder episode "The Breakfast".
- Daron Nefcy revealed this to be one of her favorite episodes.
- When Star slides on her boot in front of Marco, the shot is set up to look like the famous Mrs. Robinson seduction scene from The Graduate.
- August 2, 2015 (Canada)
- August 6, 2015 (United Kingdom and Ireland)
- August 18, 2015 (Australia)
- October 2, 2015 (Latin America)
- October 12, 2015 (Turkey)
- October 26, 2015 (Poland)
- November 21, 2015 (Spain)
- January 7, 2016 (Israel)
- January 10, 2016 (Portugal)
- April 24, 2016 (Japan)
- May 20, 2016 (Southeast Asia)
- December 30, 2017 (Philippines)