Line of Duty viewers were left reeling after Sunday night's dramatic episode ending...
She was working under the orders of the OCG gang leader who has been using her as an insider mole in the police investigation into the murder of journalist Gail Vella.
But as Kate got closer to the truth and started sharing her theories with her old AC-12 collages, the OCG were starting to panic that she could blow their cover.
More: Martin Compston - things you didn't know about the Line of Duty star
Despite having formed a friendship with Kate in earlier episodes, Jo had started to keep her at arms' length, causing alarm bells to start ringing for Kate.
But as the corrupt senior police officer - and the fourth 'H' - who is still yet to be uncovered, told Jo to get rid of Kate, she had no choice but to arrange for her to meet under the cover of darkness.
However, undercover OCG member and the newest member of the Hillside Lane team, Ryan Pilkington was hiding in the back of Jo's car.
Kate soon found herself in a standoff with Ryan, both joining guns at one another, and just before the credits rolled two gun shots could be heard.
Fans have a theory
While we will have to wait until next week to find out who, if anyone, was shot, fans have got a cunning new theory.
They're convinced that the trailer (above) for the new season, released ahead of the first episode, shows Kate alive and well in a blink-and-you'll-miss-it moment that is yet to be aired on TV.
The moment sees what appears to be a continuation of the cliffhanger ending that we saw on Sunday - with Kate and Jo standing with their hands up as police surround them.
A huge clue or a red herring?
There is also the small matter of a social media post that show creator Jed Mercurio posted on Twitter during filming last year.
The picture shows Kate wearing a distinctive purple top, which appears to be another scene that is yet to be aired in Season 6.
But could both these things be red herrings designed to lure fans into a false sense of security that Kate will be okay?
Tune in on Sunday at 9pm on BBC1 to discover Kate's fate.
Get the latest updates, reviews and unmissable series to watch and more!
Thank you for signing up to Whattowatch. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.