I missed the first episode of this three-parter last week (gutted, I was) so coming into the story one-third of the way through I expected to have some difficulty picking up the threads of the narrative. I needn’t have worried. For one thing, it soon became clear that the writer and/or director had cleverly divided the series up into establishment; realisation; fallout (that last one is a guess, but looks pretty likely given the trailers) so all I’d missed, presumably, was the back story of how Alice went missing and became Lori, together with the establishment of the two families as (a) middle class, rich, nice house, settled, but unsettled by the fact that at least one of them can’t move on after Alice’s disappearance; and (b) working class, poor, sink estate, resigned but unsettled by the fact that at least one of them knows that their child belongs to someone else.

And for another thing, the acting was so very good that I was drawn in immediately and felt like I already knew everyone within the first five minutes.

It’s perhaps unfair to single anyone out from what is an extremely strong cast all round. But you know I’m going to. Holly Aird and Jo Woodcock were simply outstanding. Their portrayal of their first meeting for eleven years – the mother who had dreamed of the moment since the day her daughter went missing, not wanting to put a foot wrong but almost incapable of holding back from the first hug; the daughter apprehensive but suddenly recognising her Mum, disjointed memories coming back in small pieces, remembering her brother’s nickname – was so incredibly accurate, realistic and moving that even though I’d only met these characters minutes before I was moved almost to tears by the scene.

ITV’s Torn webpages claim that this is Jo Woodcock’s first acting “job.” I found that hard to believe and indeed IMDb does credit her with no less than five prior performances, but even so it’s clear she’s not been around for long and to put in such a mature performance is quite remarkable.

As this second episode played out, the effects on both families of the recent events become clear. Lori’s Mum Joanna is tried, found guilty and sentenced to five years’ suspended with an order that she must never try to contact Alice. Another strong performance, Nicola Walker leaving her Spooks days well and truly behind her with this completely different role. Erstwhile father Stephen (Bradley Walsh) finds it difficult to come to terms with what’s happened, but the most significant impacts are on the Hooper family, all of whom have to adjust to Alice’s return, and none of whom manage it too well. The situation is summed up brilliantly by father David (Adam Kotz): “one of her siblings hates her, the other has a crush on her.”

Family interrelationships continue to deteriorate until finally, at a houseparty organised by Alice and attended by many of her previous school friends, younger sister Jasmine is persuaded to try drugs and ends up in hospital. David’s outburst that things have become worse, not better, since Alice’s return is overheard by Alice, who runs away in utter confusion.

How one event can play out and have so many repercussions for so many people is brilliantly explored by this excellent drama, which reaches its conclusion at the same time next week. Will Sarah and David’s fractured marriage survive the pressures of Alice’s return? Will Alice decide she was better off with Joanna and Steven? Whatever happens this is going to turn out to be one of ITV’s best drama offerings of 2007. Despite losing a million viewers since last week according to overnight figures published by MediaGuardian it still managed almost a 25% share of the audience and was at the top of the figures for its 9-10pm time slot.