Lee Hee Joon is determined to catch the mastermind behind the recent murder in town. But while investigating, he found new evidence that leads him to confusion.

Oh Bong Yi was Involved in a Murder Case and Go Mu Chi Wanted to Prove She is Innocent

The policemen are still searching for the culprit behind Kang Duk Soo's (Jung Eun Pyo) murder. Detective Go Mu Chi (Lee Hee Joon) and his team were also busy investigating the new case.

They revisited the crime scene to find leads, but it gets complicated since Oh Bong Yi (Park Ju Hyun) was also involved.

She wanted to catch Kang Duk Soo and save Yu Na from him. He has been notorious as a murderer in their town. And to stop him from committing more crimes, Oh Bong Yi faced him and attacked him until he surrendered.

But it seems like it's hard for him just to give up. He ended beating her up in the middle of a rainy evening.

IN CASE YOU MISSED IT: 'Mouse' Episode 11: Lee Seung Gi Has New Guilty Pleasures

Meanwhile, Jung Ba Reum (Lee Seung Gi) remembered Oh Bong Yi and rushed to where she was. When he saw her beaten and covered in blood, instead of helping her, Jung Ba Reum looked for Kang Duk Soo and began punishing him.

The young police officer turned into a psychopath again.

The following day, inside the investigation office, cops were also suspecting Oh Bong Yi as the mastermind behind the crime, but Go Mu Chi stepped up to prove she is innocent and isn't capable of such things.

Choi Hong Ju (Kyung Soo Jin), who is in charge of Oh Bong Yi in the hospital, was upset with Go Mu Chi for not doing his duty to protect her.Jung Ba Reum also paid a visit to Oh Bong Yi but ended up conversing with Choi Hong Ju. While they were in the middle of a conversation, the lady was shocked by Jung Ba Reum's mannerisms. They reminded her of Song Yo Han (Kwon Hwa Woon).

Days after, she noticed some similarities again between her past lover and police officer.

Jung Ba Reum Unexpectedly Left Evidence after the Murder Happen

The ruling president visited the investigation crime office to know more about the murder. When Detective Kang Si Hyeok (Yoon Seo Hyun) was in the middle of discussion, Go Mu Chi interrupted him and said he was saying the wrong information.

Go Mu Chi then started explaining his whereabouts regarding the case, with a hypothesis that the person who did the crime was a psychopath and failed to cover up some evidence from the murder.

Jung Ba Reum was having a dilemma after hearing Go Mu Chi's investigation. One more mistake and he will be caught. He needs to be more careful with his next step.

Meanwhile, after gathering all the materials, Oh Bong Yi was proven innocent. But Go Mu Chi found new information that gets him confused.

Will he already know Jung Ba Reum's hidden agenda?

ALSO READ: 'Mouse' Stars Lee Seung Gi & Park Ju Hyun Display Chemistry in New Behind-the-Scenes Video

Watch the upcoming "Mouse" episode 13 on April 15 at 10:30 p.m (KST) to know what will happen next!

Have you watched "Mouse" episode 12? What can you say about it so far? Share your thoughts with us in the comments below!

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Written by Shai Collins