Warning, spoilers ahead for Unforgotten season four, episode five

After an explosive episode five of Unforgotten, which saw our heroine DI Cassie Stuart involved in a car crash while driving home (who hit her? one of the suspects? Just an accident? Her dad?), it seems like all of our burning questions will finally be answered in next week's finale. In the meantime, plenty of fans think they have at long last worked out who killed Matthew Walsh - and we think it sounds like a good guess!

MORE: Unforgotten star Sanjeev Bhaskar solves major mystery on show

Taking to Twitter, plenty of eagle-eyed viewers suggested that DCC Liz Baildon will almost certainly be behind the death of Matthew Walsh, and they have evidence to back themselves up! One person wrote: "Omg...so Liz uses a fountain pen to write with in episode four...she’s the one who stabbed Walsh in the head. Liz is the killer, She did it for Fiona." 

WATCH: Have you been watching Unforgotten?

Another added: "I think it's the DCC. Fiona said they walked separately in the end and 15 minutes later she came across Ram doing CPR. Where was the DCC in that time? Also she would have most motive as it was Fiona who was assaulted. Just my thoughts!" 

Did Ram think it was an accident?

A third person tweeted: "Walsh wasn't dead at allotments & while driving back after car being stopped he came round in the boot. Liz used pen to finish him off then left it for Fogarty to (not) dispose of. Yes, I am working, but good drama lingers the day after." 

MORE: Unforgotten season four: why did DCI Cassie Stuart leave the police?

MORE: Inside Nicola Walker's sweet real-life friendship with Unforgotten co-star Sanjeev Bhaskar

However, another viewer thought that Fiona was the culprit, saying: "Fiona came across Walsh first, he had managed to lose the others. He was unconscious having fallen and hit his head. In a rage she rammed the pen, a hated graduation present, into the wound in his head." And who crashed into Cassie? We will have to find out in next week's episode!

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