Solution to The Investigation

This meta is a rebus, with the 10 added words being feeder puzzle answers and the 9 subtracted words being images available to solvers at the start. Solvers need to work back and forth with images and answers to (1) correctly identify the images and (2) put them in the correct order to make a functioning rebus that fits the given shell of plusses and minuses. Solvers are aided in their task by the fact that the added words are color-coded by row, narrowing down the possible places each added word could go. Of further help is the fact that each subtracted word can only be removed in one way — that is, solvers never have to guess whether to use, for example, this T or that T (when there is a double letter in the string, either can be removed, leaving exactly the same result whichever letter is considered to have been removed). The correct solution is: BIRTHDAY + STAPLER - HAT + KILO + ADDLE - DRILL - BREAD + UPCYCLE + HABIT + LONE - KEYCHAIN - LUTE - YODEL + LATHE + UNKEMPT - BLANKET - PUMP + NOLTE - CENT which gives the answer: IT'S A PLOT HOLE.