Spock and Scotty, together in the Jeffries tube. Scotty needs to make modifications to the engines with Spock's help. The lights are off and all communications are down so they have to share this tiny section of crawlspace.

Scotty is simply too hard and too turned on to concentrate on the job at hand, and if he doesn't make this fix soon, the Enterprise will blow up like a supernova.

Spock sees a logical solution.

(I'm new to this. Does this count as too much plot?)