Greg Heffley is caught in the middle as the two halves of his extended family come together in a sidesplittingly relatable summer story! When the Heffley's agree to spend summer break with both Mom's and Dad's relatives at the same time, they have to figure out how to be in two places at once. With Greg caught in the middle, can the Heffley's pull off the ultimate scheme? Or will their vacation turn into a hilarious hot mess?