What would happen if you suddenly didn't know why you married your spouse when he seemed so obviously unsuited to you? It would be confusing to say the least.

That's the plot mover in "The Birth Secret" a series due to start on April 27. The series explores a pretty basic question. What makes people a good match for each other? Is it background, shared interests, similar struggles? Are there more important criteria for a successful marriage? And if the situations change, do the people in question still belong together?

In this drama, Jung Yi Hyun played by Sung Yu Ri has retrograde amnesia and can't remember much about her life. She can't remember her husband, Hong Gyung Doo played by Yu Jun Sang , or Hae Deum played by child actress Kal So Won, the daughter they have together. Nor can she figure out why she married him.

Jung Yi Hyun is gifted with a genius level IQ and has a good education. Her husband is poor and uneducated, even though he is a loving father to their daughter, and has obviously been a good husband. What she has forgotten is the circumstances under which they met. She forgot that they were both prepared to commit suicide when they met. After sharing the pain that drove them to such desperate circumstances, they decided to face life together. And that decision was more important than any circumstances of birth and background.

During the drama, Hong Gyung Doo has the difficult job of helping his wife reclaim her memories and making sense of their life together.

It's a promising cast. Han Sing Jin appeared in the dramas, "My Husband Got a Family" and "Kang Nam Mom." He also played the character Joong Sik in the newly released movie, "Nobody's Daughter Hae Won"

Sung Yu Ri was a member of the pop group Fin.K.L. and in the last two years has appeared in the dramas "Feast of the Gods," and "Romance Town."

The drama also stars Lee Jin as Lee Sun Young and Han Sang Jin as Choi Ki Tae . Lee Jin was also a member of Fin.K.L., and it is the first time that she and Sung Yu Ri have worked together since the group stopped performing. It is rumored that Lee Hyori and Ock Joo Huun, the two other members of the group will also make cameo appearances.

Kim Jong Hyeok, who directed "Stranger than Paradise" in 2006 and "Spring Days" in 2005, directs the series. The screenplay was written by Kim Gyu Hwan, who wrote "Cinderella's Sister" in 2010, "Robber" in 2007 and worked with Kim Jong Hyeok on "Spring Days."