The Third Day is a show fuelled by questions. From the beginning of episode one, the only constant in this mind-boggling thriller has been the unknown – and although the final episode goes some of the way to tying things up, there’s a commitment to the mysterious, unstable narrative right to the very end.

If the show’s first five episodes have been a rollercoaster, episode six is one of those big drop rides which steals your breath.

For starters, Sam and Helen’s reunion offers no resolution. Sam’s reasoning for abandoning the family and remaining on Osea – to look after the pair’s son, Nathan – wears thin within moments of Helen’s arrival. The minimal sense of hope she feels at Sam’s revelation is destroyed as quickly as it’s built – the boy Sam has been looking after is not their son, Nathan (he’s way too young, has a completely different skin colour).

Helen can’t take it anymore. She hits out at Sam for “losing” their son while he was on the phone with one of his many “flings” (we now know that that “intense phone call” he described in episode two was about) and relays all the time Sam spent pursuing “crackpot theories” and accusing the people around him of taking his son. 

It’s a lot of information to take in at once, but it’s only the start of the grief-stricken relationship which plays out on-screen throughout this 60-minute adventure. 

Jess’s new baby is a direct challenge to Sam’s ‘rule’ on the island, and she’s determined to ensure her daughter is able to claim her place as leader. As a result, she’s willing to do anything to force Sam and his supporters to step aside, including violent axe murder (sorry Mr Martin). 

It’s these strange circumstances which see Sam and Helen reluctantly paired together, forced to help each other in order to stay alive. It’s a confusing dynamic – as much as you want Helen to grab her daughters and run away from Sam and Osea as fast as they can, there’s a small part of you that wants to see some kind of resolution for Sam and his daughters.

In the end, however, this doesn’t seem possible. The darkness within Sam has gone far too deep – his brutal murder of Jason with not one, but two, knives should serve as enough evidence – and the only solace he seems able to find is in the false reality of the island, where his son is alive and he is blameless in it all.

At least, we think this is a false reality. When Helen turns to leave after Sam has given her the money he stole – aka the real reason why she came to the island – the boy Sam believes to be Nathan steps forward and tells Helen not to worry about what she said to him before he disappeared (something she had lamented over in a previous episode). It’s a fantastic moment – just when you think things are reaching a resolution (at least by Osea’s standards), this remark throws everything into doubt once again.

Is Nathan really the boy standing in front of her? And if so, is everything Sam has been told about Osea true?

The uncertainty of this moment hangs over the closing moments of the episode, which see Helen escape from the island by swimming to the mainland, dragging her daughters in a boat behind her. We don’t know whether Helen is going to survive. We don’t know what is going to happen to Ellie and Lu. We don’t know what life might look like for Sam back on the island. And we don’t know whether Osea really is the “special” place the islanders claim it is.

But as Helen, Ellie and Lu huddle together for warmth on the floor of an abandoned cabin, there’s something oddly comforting about the questions which are left to hang over the narrative. In a series obsessed with the power of the mind, the viewer is given the choice to choose what we believe – and it’s that sense of freedom which makes The Third Day so special.

Episode six of The Third Day airs at 9pm tonight on Sky Atlantic.

All episodes of The Third Day are now available to stream on Sky Go and NOW TV.

Images: Sky