The Undertakers - Season 1 Episode 2

That ring 's sold to Sieun's classmate in the secondhand market. She see Si-eun's ghost every night and suffers from fear,too. Sang-jo finds out that she fell in love with teacher and she died pregnant. Sang-jo blamed him but he denied their relationship. After a while, that teacher was found crazy ,wearing the same ring as her.What 's the secret of the ring? Why did she commit suicide?