I was all ready to make fun of The Ark (Monday, BBC1, 8.30pm), the BBC's retelling of the old biblical story of Noah and the great flood.

I was going to point out that, in this new version, Noah appears to be from Manchester rather than Mesopotamia (which is presumably why he's played by David Threlfall from Shameless).

I was also going to point out that, if we are to believe the BBC retelling, there was room on the ark for non-essential items such as hair conditioner. Which is why when the Almighty wreaked his vengeance on an ungrateful earth by cleansing it with an apocalyptic flood, Mrs Noah's hair looked so radiant and lovely.

And finally, I was going to point out that, according to the BBC version, Mrs Noah wasn't really into the whole ark idea anyway. In fact, she asked some of the basic questions that would occur to anyone when faced with the animals-on-a-boat thing. Like: won't they all eat each other?

But then I actually watched The Ark and the desire to make fun of the silly voices and the unfeasibly lovely hair disappeared; it was swept away. Threlfall's accent did take some getting used to, but it didn't matter much because something unexpected happened very quickly, something that was particularly surprising for an agnostic like me who finds the Old Testament difficult to say the least. This strange, unfamiliar piece of television based on an old, troubling story about God punishing mankind moved me. It made me cry.

So how on earth did that happen? I think the answer is that, at a time when TV and film seems obsessed with magic, the writer of The Ark, Tony Jordan, did the opposite and took almost all of the magic out of Noah's story and presented a much simpler tale about what a family would actually do in a situation where the father suddenly, out of nowhere, said God had told him to build a giant ship.

There was a bit of magic in The Ark - of course there was - but it was rather beautifully and subtly done. When God's messenger appeared to Noah, there was no thunder, no Brian-Blessed voices and no beards. Instead, an ordinary man walked into Noah's life, and as they both sat in the sun, he explained what it was Noah had to do.

It was what happened next that was particularly moving. Noah passed on the message from God to his wife and children, and their first reaction was predictable: don't talk such rubbish, we should work on the farm rather than build a boat for a flood that will never come. So Noah started working on the ark himself, working until his hands bled and his legs buckled.

Eventually, it was his wife who changed things, telling her sons she would help build the ark not because she had faith in God but because she had faith in her husband. And so, suddenly, Noah's hands on the giant planks of wood were joined by the hands of his wife and those of his sons. It was a simple but profound moment that, suddenly and unexpectedly, got to me and made me cry.

It is also probably how Bible stories should be done on contemporary television. The Old Testament is a million miles away from us, but, with a turn of the dial, it can be brought much closer. Bring out the ordinary situations that are sometimes hard to spot amid the instructions for building tabernacles and the lists who begat who and suddenly the importance, and the power of it, is clear. That's what Tony Jordan has done with The Ark. I'd very much like to see him do it again.