The Hogtied.com version of a three-legged race is a six-legged race ... and it's WAAAY harder than a three-legged race. Image source: Hogtied.com.
Alternatively: The thing that made their hearts beat faster was that he had told them he had left to go to the store and get MORE rope!
Alternatively Alternatively: (ONe day about a year from now) "I HATE the way Hollywood COMPLETELY ignored the story in 50 Shades of Gray, but some of the imagery WAS nice." (Bret Easton Ellis is very eager to do the screenplay for 50 Shades of Gray, I can't imagine a person less likely to do a good job, or to understand the underlying appeal of the story. If he writes the script, look for something like this.)