OK, caught up with the episodes I was behind (lockdown has to be good for something, right?) so am going to annoy you all but getting my head straight on here before the final episode:
Eight years ago, Earlham (already a doctor at that point) was at work when he stopped to chat to a junior colleague who had had a nasty date the previous night (possibly spiked? Earlham offered to do a blood test to check) and left his jacket at the man's flat. Earlham offered to go to the flat to retrieve the jacket and met Oliver. He later returned to put cameras in Oliver's flat and learned of his habit of drugging and raping young men. He used the video evidence of this to blackmail Oliver into giving him a supply of date rape drugs, and we presume his first victim was his ex, the bartender.
We also learn at this stage that Earlham was married with a young son but that he visited prostitutes and made them pretend to be completely unconscious while he had sex with them. However, once he saw Oliver's rapes, he realised that the pretence didn't turn him on any more: he wanted the real thing.
Meanwhile, eight years ago, Laura was fulfilling her dying father's wishes by giving him a drug overdose so that he died rather than persisting in his vegetative state. She put the necklace he gave her into his hand.
Flash forward to three weeks ago and we realise that Earlham - who blames Laura for all that has gone wrong, but especially his son's suicide attempt - is planning to fake his own death and frame Laura for it with the help of Oliver. Oliver collects the car key from hospital lost property (where the sister handed it in) and puts it into Laura's flat, and he also takes blood from Earlham. When the police break into the shipping container, they find the staged scene - Earlham's hideout (the sleeping bag), a lot of his blood, and Laura's necklace.
Mystery: how do we get from that to Earlham lying in the marshes with his throat slit?
Mystery: why is Oliver still hanging around in the present day, after Laura's arrest, etc?
They also know that Laura's satnav places her car at that shipping container. Laura knows she never drove there so realises she's been framed by someone in the police because they impounded her car. She steals Maxwell Snr's phone, miraculously guesses his pin on the third go, and finds an email that proves that Maxwell Jnr is a cop who's also a cocaine addict, and the dad is being blackmailed - frame Laura or the son gets exposed. Rather unbelievably, the dad is happy to go along with this rather than actually investigate the crime of blackmail.
Oh, and in a late attempt to make us care about Woman Detective and forgive her for not just the nicotine gum but how shite she is at Detective-ing, they gave her a back story of an evil abusive partner who is now out on bail and has already murdered someone.
Mystery: is this relevant to the main plot or merely a shameless attempt to make her less one-dimensional?
Main Suspects:
the son, who told his counsellor he would kill his father if he saw him again.
Oliver, who was probably tired of being blackmailed by Earlham.
BIL, who seems to hang around for no good reason and therefore is very suspicious.
Laura.
Less Main Suspects:
Jill Halfpenny, who seems to have disappeared.
Wife of Jill Halfpenny, who seems to have put herself into self-isolation ages before anyone else did except for her little visit to the car pound.
Sister of Laura, who runs around now like she's Nancy Drew.
Porthos, who began as a strong contender but is now miserably loafing around brooding about being charged for burning down his own property.
Mrs Porthos, who is actually so sweet and innocent that I think she might come up on the outside and win the whole thing.
Phew! What have I missed?