Picture two sisters, both 28. One of them, Seo Ji An (Shin Hae Sun), is a responsible daughter with a flinty edge. After pushing herself hard for two years to be confirmed as a permanent employee in a chaebol, she is reaching breaking point and losing her patience with social superiors who trample on her pride.

The other, Seo Ji Soo (Seo Eun Su), is flakier and happier. Lately, she has been stalking two men in the neighbourhood - a baker she hopes to work for and a furniture-maker she has a crush on - with the determination of a teenage fangirl.

If you were their mother and a posh, ferocious woman were to burst into your home, claiming one of your girls to be her long-lost daughter, whom would you give up?

My Golden Life is a rich melodrama springing from that moment between two mothers. The early episodes set up a rather predictable Cinderella story, as Ji An prepares to move in with her newfound family, the people who happen to own the company she works in.

But the show soon gets into a fascinating mess, when it turns out that her mother (Kim Hye Ok), who has the manner of a frightened rabbit, managed to lie to her domineering caller. Ji Soo is the real heiress to the chaebol, which makes Ji An an unwitting impostor.

Ji An is packed off to that household in the hope that they can give her what her own parents couldn't - a chance to start over, live her dream and go to an art school overseas - but her mother's scheme might collapse like a house of cards.

My Golden Life is the latest family drama in South Korean broadcaster KBS's golden weekend slot, though, so it's safe to assume that over 50 episodes, regrets will be expressed, lessons will be learnt and misunderstandings will be melted away.

But it's also the handiwork of So Hyun Kyung, the writer of Seo Yeong, My Daughter (2012) and Brilliant Legacy (2009), and its story turns out to be almost as deeply conceived as those.

The tale of sisters who are switched by their mother might not be surprising in outline. Neither is the web of romcom storylines linking the sons and daughters of the two families. At close range, however, the show has sensitively drawn characters, emotional details and family histories that invite you to go even closer.

Like Seo Yeong, My Golden Life looks into how pessimism can be passed down from generation to generation.

Ji Soo is less resentful of the Seo family's poverty than Ji An, possibly because she was brought up as the favourite daughter and never had to shoulder the family's financial burden. But you will wonder if it is also because Ji An has inherited the negativity of her mother, who still hasn't forgiven her father for his business failure.

"People live because of people," her father advises her brother, who is afraid to take the plunge and get married because they are broke.

And I'm watching this because of them, people who are so unhappy but so alive.