The plot was:
Part I
In Part 1 of the two-part series finale, Spencer offers to take Carly to the Air Force father-daughter dance because their Dad, Colonel Shay, isn't able to accompany her because of his overseas deployment. Spencer gets ill and can't take her, so Freddie and Gibby offer to take her to cheer her up. Elsewhere, Sam and Spencer rebuild a motorcycle (as mentioned in Jennette's Time for Kids interview); and Freddie obtains a new Samsun Gemini Maxpad.
Part II
Conclusion. Colonel Shay surprises everyone by arriving just in time to be able to take Carly to her special dance. They return from the evening and Carly is disappointed to hear that her Dad must go back to Italy that night and she is put up to a difficult situation/decision.