Our protagonist is one Eddie Baxter, an ambitious competitive dancer who hopes to win a contest on Broadway which would kickstart his Hollywood career. Unfortunately, he can't find a female dancer partner who meets his exacting standards. Finally, he notices an advertisement in the newspaper:
Eddie feels he's found more than just a winning dance partner - as days of rehearsing commence he tries to strike up social encounters with Marla as well. However, while Marla is happy to spend the day with him, she always parts ways before evening.
Eddie happens to notice Marla doesn't sunburn; she claims she has a very good skin lotion.
As the day of the contest nears, another dancer suggests Marla has a boyfriend and she'll stand him up. However, Marla comes through for Eddie, arriving on time for the contest, marking the first time Eddie has seen Marla in the evening. They go on to win the contest, just as Eddie hoped. However, Marla won't stop dancing! She dances Eddie right out of the theater and into the darkness. Her secret finally comes out...
Marla finally explains she was killed by Ando, who claimed she was full of "intrigue." Marla doesn't believe this, maintaining she's an innocent woman who just wants a dance partner...someone she can dance with for an eternity. She's chosen Eddie as that partner.
It's interesting to note Marla moves about during daylight hours with no ill effects, which is contrary to most vampire stories, but wasn't exactly "codified" back in '51. Protagonists in early Atlas horror stories usually possess a flaw which causes them to "earn" their deaths (because the protagonists nearly always die); in Eddie's case, his being picky about dance partners is the flaw...otherwise, he's an innocent victim. Or, despite his declaration of "doomed!" perhaps he made out all right by becoming a dancing vampire. In which case...it's a happy ending!