Who Killed Sarah tells the story that 18 years ago, the Lascano family framed Alex for murdering his sister Sarah to save their reputation. Now, Alex, who ended his prison life, began his revenge plan.

Alex, the male host, and a group of friends took Sarah to the sea to play paragliding, but during the play, Sarah's parachute rope suddenly broke, and Sarah fell into the water from the sky and died on the spot.

Alex was unjustly imprisoned and released after 18.

After he got out of prison, he was bent on getting back at Rudolph Lascano, who created the murder and led to an unfair judgment against him.

However, Alex has feelings for Eliza, the youngest daughter of the Lascano family, and things become complicated.

He found that Rudolph was innocent, and another person cleverly hidden in the dark was the culprit who made him feel wronged.