Ryu Jun-yeol’s curiosity led him to the original webtoon for Netflix thriller ‘The Rat’

Ryu Jun-yeol said he could not guess what would happen next while reading the scripts for Netflix’s new thriller “The Rat,” so he sought out the original Kakao webtoon himself.

The 10-episode suspense series follows a reclusive novelist whose name, face and entire life are taken by a mysterious presence. Its premise draws on a Korean folktale about a rat that eats fingernails.

Ryu plays two roles for the first time: the novelist, Je Moon-jae, whose life has been stolen, and the “rat” that takes his name and appearance. He said the challenge was not making the characters dramatically different, but persuading viewers to believe they were separate beings even while knowing the same actor played both.

Rather than making the performances overly broad, Ryu used differences in gaze, personality, voice and speech. He said the voice would be especially important, with telephone scenes likely to make the contrast clearest.

Director Kim Hong-sun said he liked the original work’s cold sense of horror, while writer Lee Jae-gon expanded it into a faster chase narrative. Seol Kyung-gu plays a moneylender trying to recover lost funds, and Lee Kyu-hyung plays a detective investigating the rat’s identity. The three characters become entangled through the same incident.