There are several components to this puzzle:
Solvers may notice there are always 22 letters in the capitalized words from each detective. These words are in fact telling you the stations the detectives visited over the course of the game. In conjunction with the given starting location tiles, you can uniquely determine the path taken by the detectives over the course of a game of Scotland Yard. Given the detectives’ paths, Mr. X’s token board and the fact that Mr. X was never caught in the course of the game, you can also uniquely determine the path Mr. X took on the game board. The paths of all 5 detectives and Mr. X (in red) are shown in the below image. Bear in mind that on two turns, Mr. X was able to move twice in a row.
After solving for Mr. X’s path, the stations he visited spell out SUBMIT THIS ANSWER LEAVES BE. LEAVES BE is the answer to this puzzle.