In The Line Of Duty ~The Spy Who Loved Me~

Sometimes one is called upon to go what others might call, far and above the call of duty. For Mr. Spock this became one of those times, although one might consider it not. As with all things in love and war, things are always in flux, transforming, evolving, and one is forced to adapt, make modifications and revisions at a moments notice. So it was, that while Captain Kirk made his escape from the Romulan brig, beamed back to the Enterprise, had Doctor McCoy perform temporary reconstructive surgery on him so that his facial features where that of a Romulan, dawn a Romulan uniform, and then beam back aboard the Romulan vessel. It then became Spock’s job to keep the Romulan command occupied. This was a task made all the more easier due to the commander’s strong attraction to Spock, as well her willingness to do what ever it took to capture the Enterprise intact and bring her back to the Romulan home world.
But as with all things there are always unforeseen consequences