Lucy says she's got things under control, but she still needs Matt and Emma's help to restore the life support.
[See puzzle page for additional images.]

3 of the 4 letters are in the first half of the alphabet.

These letters are all different letters in my favorite U.S. national park, which is known for its buttes!
The uppercase missing letter contains a vertical line.


None of these letters are on the bottom row of a QWERTY keyboard.


If I added eyes, the missing letter could be a happy face!
Multiple of these letters are Roman numerals.


The missing letter is in the first 5 letters of the alphabet.

The missing letter is an odd prime with A1Z26.

The missing letter is one away from an existing letter, using a Caesar shift.
The Caesar shift is backwards.


The uppercase missing letter has all straight lines, but no right angles.
These letters are all pentominoes.


The missing letter is a multiple of 4, using A1Z26, that isn't already used here.

None of these uppercase letters have rotational symmetry.

Old MacDonald sings about the missing letter.
One of the letters is repeated.


The letters together do not spell out a U.S. state.
The missing letter is a vowel.


These are 4 out of the 5 letters I use in my Wordle opener.

Matt uses a bird for his Wordle opener.

If you add "i", the letters spell a verb.
The verb is present tense.


The verb is related to eating.