Plot holes *SPOILERS*

Just watched this.

OK, so Kate was Sophie's real daughter and Mara was an imposter, as others have pointed out. It was a silly and pointless second twist raising two plot holes.

Firstly: surely in the 21st century no one lets a stranger into their family without a DNA test. There are inheritance and next-of-kin issues to be legally determined. "I am her mother" may be a throwaway phrase to a nurse, but in family law it has to be proven especially in a case such as this.

Secondly: the same authority that sent Mara the letter after contacting her real mother knows the identity of Mara's mother, so it would be easy to find out that it isn't Sophie.

Really we must assume that an author and an architect are both acting dumb and didn't go for any of the above.

5/10.