The Daily Printable Giant 150-Word Mystery Fill-In Puzzle is our most challenging daily English language fill-in puzzle. In fact, we can say with confidence that it is by far the most challenging daily English language fill-in puzzle available anywhere. It incorporates many of the quality enhancing features found in our other fill-in puzzles. The puzzle is comprised of words from three to eight letters in length. It is designed to be a bit more challenging than most fill-in puzzles in that the eight-letter words will never cross each others path in the puzzle grid. The same is true for the seven-letter words and also for the six-letter words. As an added challenge, the puzzle will always contain a number of Mystery Words, which are never shown in the puzzle's word list. In the above puzzle, for example, all of the -letter words are Mystery Words. Correctly fit all of the listed words onto the puzzle grid to reveal the Mystery Words. Need help? Click the blue question mark to add a starter word before printing.