I have admittedly been drinking many 
& Ts.
Oh, gin, why do you make me think such twaddle?
But how's this for crazy plot twist:
- Small kid James was brought up in Liverpool by his Dad, who split from his Mother after she became pregnant as a result of an affair.
- With man who is Paula's Dad!
- The resulting baby was GarageCallum!
(so only Paula's
half brother, biologically, though neither are aware).
- Paula's Mother reluctantly agreed to bring up GarageCallum as their own, after his own Mum was rendered incapable by something (Severe, ongoing illness? Serious brain injury after vicious attack by jealous Paula's Mum, who was then consumed by guilt/ pressganged into it by her husband).
- James's DM has needed intensive nursing care ever since.
- Small James was kept unaware of it all. Since the divorce, he has only ever known and visited his Mum in medical settings, so that is their norm.
- Traumatically, adult James uncovered/ was informed of the lies, which has induced violent rage/ jealousy/ desire to seek revenge etc:
That he'd been deprived of a DM (who had chosen cheating on his DF, and thus James's best interests, above loyalty to them both).
That, conversely, his (hitherto-unknown about) baby half-brother GarageCallum (now perceived as partly responsible for the fracturing of James's family) was brought up by 2 'loving' parents, one of whom had ruined James's parents' marriage.
And had the luxury of a sibling.
- We know different: Paula's/ Callum's Dad apparently temperamental and not to be upset at all costs, Paula's/ Callum's Mum (secretly actually his StepMum) appears cold and not exactly brimming with compassion. Difficult dynamics all round, from both.
She definitely shot Paula a 'here we go again'-type expression re
"Bad dreams: can I stay here tonight?"
"OK. Just don't upset your Father"
WTF, why wouldn't you sit down with your DD and find out more/ comfort her?
Bad blood between them.
Callum off the rails. Perhaps resented all his life for being a reminder of OW? Blamed for childhood camping knot strangling incident, even though Paula instigated it?
Suspect he'll regain consciousness to share some vital detail about probable arsonist murderer James.
(Or do we really believe it was a suicide attempt/ accident with his Primus stove?). 
Doesn't explain how ScarySewn-UpMouthGirl fits in, though.
Or Crystal/ Morgan?
(Am sticking with my theory that Morgan was abducted).
Sidenote:
Paula, for the love of God, buy some water and stop knocking back your tablets dry.
(Why do tv characters always do it? How do they do it? Have you ever tried it?...it's horrendous).
I promise never to post again on MN, whilst under the influence.
Sorry all.
Was nice though 