Thread of Lies (; lit. Elegant Lies) is a 2014 South Korean film based on the 2009 bestselling novel "Elegant Lies" by Kim Ryeo-ryeong. Directed by Lee Han, it starred Kim Hee-ae (in her first film in 21 years), Go Ah-sung, Kim Hyang-gi and Kim Yoo-jung.
Kim Hee-ae was in a movie in the 20th century.
The excerpt explicitly says that a movie in 2014 was Kim Hee-ae's first in 21 years, meaning she must have been in a movie before the year 2000.