
The return of Line of Duty featured a worrying clue that some viewers might have missed.
Jed Mercurio’s drama returned for a sixth series on Sunday (21 March), and the episode contained a few Easter eggs for fans to ponder over before the next outing.
The latest series centres on DCI Joanne Davidson (Kelly Macdonald), who is under investigation by AC-12 due to her behaviour during an investigation into the murder of a journalist named Gail Vella.
It’s Joanne’s fellow team member and former romantic partner, Farida Jatri (Anneika Rose), that brings this to the attention of DS Steve Arnott (Martin Compston).
Confusing matters is the fact that DI Kate Fleming (Vicky McClure) has left AC-12 and is currently working alongside both Joanne and Farida, building trust from the ground up following her past uncovering police corruption.
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In a scene in which Steve informs Kate that her team is being investigated, he sends her a text to let her know he’s nearby. When she leaves the station, she looks up and Steve flashes his car lights.
However, fans noticed that Steve flashed them four times, which is morse code for the letter H.
This could just be a coincidence, or even a funny piece of misdirection, but viewers are especially worried considering the identity of the fourth and final officer making up the league of corrupt officers known as “H” is still at large.
Hilariously, Kate herself criticises his use of this signal, undoubtedly due to the fact she knows he just indicated “H” for all to see. “First thing that came to mind,” he responds – but could Steve be bluffing her?
The fact that morse code was used here is intentional considering that previous H revelations have been revealed using morse code.

Fans on the hunt for spoilers of what’s to come also noticed a QR code on a magazine prop and were surprised to discover that scanning it using their phone led to some big clues, one of which involves – you guessed it – morse code.
Could Steve have been working with DI Matthew Cottan, ACC Derek Hilton and legal counsel Gill Biggeloe? Time will tell.
Line of Duty continues Sundays at 9pm on BBC One. Read our review of the show’s return here.