Warning: This list contains spoilers for the first five episodes of Hawkeye.
There are many intriguing mysteries in the MCU Hawkeye streaming series, and one of the most fascinating is the slow tease that Laura Barton is not what she seems. Many clues point to her being a possible version of Mockingbird, the former West Coast Avenger and undercover spy from Marvel Comics who was also married to Clint Barton for a long time.
Over the course of the series so far, Laura has slowly revealed that she not only has a working knowledge of Clint Barton's life as an Avenger and S.H.I.E.L.D. agent, but has her own set of skills and hidden secrets. All of these clues tease the fact she could be Mockingbird, who has yet to appear in the MCU proper thus far, though a version of her did appear in the Agents Of S.H.I.E.L.D. television series.
The Avengers Never Knew About Her
Clint Barton was especially cagey about his past and life outside of the Avengers, and Avengers: Age Of Ultron made clear why. "Fury helped me set this up when I joined," Clint told the others after taking the entire team to his rural home. "He kept it off S.H.I.E.L.D.'s files." At the time, the assumption was that keeping it off the books was for Clint's benefit, but Clint is a public figure.
The fact that no one knows of Laura Barton's existence is a clue that she is not who she says she is. Mockingbird is one of the most important spies in Marvel Comics, and it's possible that Laura is actually undercover still for reasons yet to be explained.
An Agent Of Some Kind
In retrospect, there were subtle clues to Laura's eventual identity. When Clint first introduces her to the team in Age Of Ultron, Tony Stark says "This is an agent of some kind." Clint doesn't deny it or acknowledge it and instead says, "Gentlemen, this is Laura." Tony Stark is one of the most perceptive people in the MCU and his assumption seems to have been on the money.
The fact that Laura's concern in the Hawkeye series extends to her children as well is also teased in Age Of Ultron. When the Barton children run into the living room, Tony says "These are smaller agents," another bit of foreshadowing to the Barton family secret.
Laura Knows Spycraft
As the Hawkeye series has progressed, it's become increasingly clear that Laura has a working knowledge of spycraft. In her conversations with Clint, she reveals an understanding of covert spy and agent tactics, like "catch and release" from episode two, as well as operative knowledge of outfits like the Tracksuit Mafia.
Comic books fans know that Hawkeye was married to Mockingbird for many years, as he is to Laura in the MCU. Laura could certainly come by this knowledge through osmosis just being married to Clint, but more clues reveal that she has a far deeper understanding of espionage than should be expected.
Laura Performs Spycraft
The biggest indicator that Laura is some kind of spy or agent comes in episode 4. Clint asks Laura to look into Sloan LTD., a shell company he and Kate Bishop discover is connected somehow to the Tracksuit Mafia. Laura discovers - through means the audience doesn't see - that the company is actually run by Jack Duquesne, the fiancee of Eleanor Bishop.
It is simply impossible for Laura to have come by this information unless she is a working undercover agent with contacts in either S.H.I.E.L.D. or the criminal underworld. She is either a former agent, now retired, or as the series seems to suggest, still deep undercover.
She's Super Concerned About The Watch
Though the primary concern at the outset of the series is the theft of the Ronin costume and the possibility Clint's role as the vigilante could be exposed, it's even supplanted by concern over the watch stolen from the Avengers compound. Laura telegraphs her concern about it when she asks Clint if anything was stolen from the compound beside the suit.
She also doesn't want her kids to know she's asking about it, speaking in German briefly to Clint over the phone. This seems to catch Clint off guard, and he looks around to see if anyone is following close behind. Laura could possibly be German in origin, though Mockingbird in Marvel Comics was American.
The Watch Belonged To Someone Under Cover
Laura's concern about the watch quickly becomes Clint's concern. He tells Kate Bishop that the watch belonged to someone who is still undercover. This person is a 'friend' who has been 'out of the game' for a long period of time. No one knows who they are or where they are.
All of these aspects of the undercover agent apply to Laura. Though it could conceivably belong to someone else, Laura is able to track the signal the watch emits, meaning she is familiar with it. Why Laura is undercover or what the watch has to do with her past remains unknown.
Kate Found Laura's Name Next To The Watch
Comic book fans know Echo is a powerful and frightening enforcer for the Kingpin, so the fact that Kate Bishop found a list with Laura's name and the Barton children's names in Echo's apartment is not good. The list was lying next to the missing watch, directly linking the two.
How Maya Lopez would have derived the Barton family's name from the watch remains a mystery, but it's another solid clue that Laura and the watch are connected. Laura is likely an alias, and she could be revealed to be Bobbi Morse, the real identity of Mockingbird in the comics.
Laura Knows Who 'The Big Guy' Is
While Laura would be expected to know some aspects of Clint's life as an Avenger or S.H.I.E.L.D. agent, it's unlikely he would reveal operational secrets to her. One of those is the identity of the 'big guy.' Fans now know that this is the Kingpin, and Laura has known this the entire time.
Wilson Fisk has gone to tremendous lengths to keep a low profile, meaning she wouldn't just know him from the news. Given Fisk's interest in the watch, she may know him very well, and they could have had some kind of encounter in the past.
Mockingbird Hasn't Been Revealed In The MCU Yet
A version of Mockingbird does exist in Agents Of S.H.I.E.L.D., with actress Adrienne Palicki playing Bobbi Morse in the show. The canonicity of the show remains in doubt at the moment, but even if the show is confirmed to be part of the MCU, it doesn't preclude Laura from being Mockingbird.
Just as there are many versions of Hawkeye in Marvel Comics (and presumably in the MCU multiverse) there could be multiple versions of Mockingbird. Mockingbird may also be a codename that multiple people utilize, passing from one to the other.
"We've Been So Careful"
Laura's concern about the watch and Kingpin comes to the fore in episode 5. In her conversation with Clint, she tells him "We've been so careful" and they're "so far away" from the city. This suggests that she and Clint have worked hard to maintain their deep cover and a big reason they're on the farm is to be as far away from New York City as possible.
This also suggests Laura has some larger connection to Kingpin or the world of organized crime that is yet to be revealed. Laura could have been an agent who took down elements of the Kingpin's organization in the past and had to go underground to stay alive.