Disappointing and not believable. These are my observations (in no particular order)...
Tom looks much older than 4 in the flashback.
Jodie said she took her eyes off him for 30 seconds- it was a good ten minutes!
Why didn't the brother face Tom when taking his phone call - why did he turn his back?
Why wasn't the brother soaked from pushing the body out in the water?
Why didn't the brother challenge the cheating husband instead of turning a blind eye?
As if anyone would go into the woods to have some fun time with their wife's best mate, near their wife's entire family!
How do you get a job in a school with no teaching experience, or even get an interview for that matter?
Then only focus on 1 student?
Why not just get a DNA test / take a photo of the boy straight away?
How did Daniel's father recover from being racked with a steel rod so fast?
Pointless subplot with the fake documents and kid gangsters on bikes... went nowhere!
Why did Daniel's dad not kick off to the police more?... he's lost his son, his car, had his window smashed, been hit over the head etc?
Why wasn't Jodie apprehended for any of this regardless of the DNA result?
Did Jodie's dad know about the drowning... is that why he killed himself in the bath?
Why would anyone adbuct a child and live in the same area? They wouldn't.
Why couldn't Daniel's dad just explain his wife's death to Jodie earlier on?
Why was Kate so involved with her husband's ex-wife's family?
The DNA test swapping - so far fetched
The way Jodie treats her business partner and gets away with it?
Knowing that passport checks are all electronic nowadays - how can anyone counterfeit one in 1 night?
And the accents...posh mum, Lancs son and Geordie daughter?
I could probably go on! It had such great potential and good actors. A case of all the gear, no idea!