The Replacement: YOUR best theories about what Paula is up to

Naturally, tweeters – and RadioTimes.com readers – are leaning towards the latter (after all, what would this drama be if it was all in Ellen's head?). And they have plenty of questions. Like...

Is Caris really Paula's daughter?

Katie Knight reckons Paula is actually her step mum and that she can't have children herself.

"I think Caris is alive but not actually Paula's daughter; maybe she's Kirin's from another marriage. Maybe Paula can't have children and that's why she's so obsessive with Ellen and Leah, and possibly Paula behaved the same way with Georgia. This leads me to think that Paula didn't kill Kay, and there will be a surprise twist ending when we find out who the killer really is. It could be David, Ellen's husband, Kirin, who knows!"

And Twitter agrees...

Caris is not Paula's child #Thereplacement she can't have children!

— Elise (@Rainbowpeas3) March 8, 2017

Did Caris die?

"I think Paula's daughter died years ago but lives her life imagining she is still alive. Not sure who would the young girl Ellen met be tho."

– Camille Crozier

Twitter is certainly behind this theory, with endless viewers tweeting their hunch that Caris is no more – a suggestion backed up by the fact that Paula manages her daughter's social media accounts.

It certainly brings a whole new meaning to the term "the replacement"...

"It seems too obvious that 'The Replacement' is referring to Paula's desire for a new daughter 'to replace' her deceased one. (In addition to the obvious maternity cover). I hope there is a good twist."

– Jennifer Singer

Or is everyone simply looking out for Ellen?

Kathryn Riley is choosing to see the best in Paula and her husband – but we're not so sure...

"Was Kirin talking about Ellen and not Paula when he was discussing somebody he knew with mental health issues who was struggling to accept reality? Did Ellen's husband set his wife up so he, Paula and Kirin could help her? Very strange how he left his wife with Paula by herself."

Has Paula done this before?

We quite like the theory that Paula is a serial maternity coverer and baby stealer. Is that why Georgia is so shifty with Ellen?

Or... is Ian the real baddie?

#TheReplacement Ian and Paula a couple both psychiatrist lost a child? Can't have any more? Set Ellen up to have their own baby? My theory.

— KELZO14 (@DLYTFULDIVA) March 7, 2017

The Replacement concludes next Tuesday at 9pm on BBC1

Got a theory you'd like to add? Share it in the comments box below...