Author's Note: For the epistolary square on my trope bingo card.

All the Words Big Enough

A sticky note on Agent Natasha Romanoff's side table by her bed, tucked underneath a silver arrow necklace the morning after Agent Clint Barton leaves for a deep cover mission that will "take time."

At the top of the sticky in very small letters: To say how much I'll miss you.

There is nothing else on the note.

A pair of two notecards at the bottom of Agent Clint Barton's duffel bag, found aboard the Quinjet in transit.

On the outside of the first card is written: To make the time pass quickly.

The inside is blank, and so is the other card.

A service order slip attached to Captain America's shield, plucked from Steve Rogers' fingers by Agent Natasha Romanoff.

In the description field is scrawled: To convince you to not get attached.

The rest of the fields are blank.

A notecard delivered to the desk of Agent Natasha Romanoff, care of SHIELD, three weeks into Agent Clint Barton's undercover ops in Nairobi and one week into her new partnership with Steve Rogers.

On the front, neatly handwritten: To lament the state of my comms.

The inside is completely blank.

A postcard taped to the refrigerator door at Agent Clint Barton's next scheduled rendezvous in a SHIELD safehouse.

On the back, written in pencil in an elegant cursive: To cover breaking in a new partner.

The front is completely white.

An extra sheet of printer paper attached to Agent Clint Barton's next mission brief, which is mysteriously lying on Agent Natasha Romanoff's desk instead of where it should be.

Scrawled in sharpie marker on one side of the page: To cuss out the big boss.

The other side is completely blank.

An encoded attachment to the secure email from SHIELD with Agent Clint Barton's next set of orders concerning this long-term deep cover assignment that just got longer.

The excessively long file name is For-the-last-addressee-to-placate-me-for-his-complaints-about-SOP.

The file itself is empty.

A sheaf of handwritten papers in Agent Phil Coulson's handwriting, filed under Strike Team Delta before it is removed by Steve Rogers for safekeeping (and help with this whole partnership thing).

Somewhere on the third sheet, a random note reads, "Decryption code: All the words big enough."

A USB drive packed in with the latest batch of confiscated equipment Agent Clint Barton ships back to SHIELD headquarters.

When plugged into a computer, the drive is named "To fill the empty spaces."

There is no data on the drive.

A sheet of notebook paper in the weapons cache Agent Clint Barton was instructed to raid for supplies.

On one side is neatly typed: To compare hands to jewelry.

The rest of the lines are empty.

A text message on an untraceable, unhackable Starkphone in Agent Clint Barton's gear.

To protect you: .

His op is abandoned. SHIELD goes down. They aren't agents anymore.

A whisper in Natasha Romanoff's ear when Clint Barton finally slides his weary, tired body into a safe bed in the Avengers Tower.

"To return the favor."

She shudders, and he softly kisses away the tears she will not shed.