As "The Silent Sea" reaches halfway through the first season, Gong Yoo, Bae Doona and the rest of the team find out the truth behind the top-secret mission.
Despite the government blocking them from receiving vital information regarding the lunar expedition, Song Jian learned that the Republic of Korea's Space and Aeronautics Division (SAA) wants them to retrieve samples of "lunar water."
'The Silent Sea' Episode 4: Restoring the Communication Signal
As the team moves in groups, Captain Han and the rest of the male crew tries to reconnect the communication line.
Han Yun Jae moves down to the elevator shaft, hoping to restore the signal. Unfortunately, the elevator begins to ascend and just in the nick of time; he manages to get out and move to a much safer area.
However, Captain Han is still at risk as one part of the station almost hit him, which got him hanging upside down.
Due to the impact, his oxygen system got damaged and he needs to get to the station immediately before he completely loses his oxygen supply.
READ MORE: 'The Silent Sea' Episode 3: The Mysterious Virus Begins to Worry Gong Yoo and the Rest of the Elite Space Crew
As he heads to the station, he suddenly collapses, but the rest of the team manages to save him and replenishes his oxygen immediately.
"The Silent Sea" episode 4 showed that one of the crew members happens to be a spy.
It came after the team got a communication signal outside the station and appeared to be emanating from storage 3, where the dead body of co-pilot Lee Gi Su is at.
At first, the crew thinks that it might be the intruder; however, it turns out that Gi Su is working for the RX.
This is also the main reason why Captain Han decides to hide some information from its members.
Song Jian Detects the Virus
Initially, Song Jian believed that the incident that killed Gong Soo Chan was not a virus or bacteria since the body shows no traces from it.
Interestingly, she tested her blood and a specimen from the capsule and learned that the water can quickly multiply and would only stop once the host dies.
With this, Song Jian warned the team about the possible effects of the substance found in the capsule.
"The samples we're here to retrieve, is it water?" she asked the team leader.
From the looks of it, it appeared that Captain Han knew something about the expedition.
Song Jian questioned why he had to keep it a secret, but Han Yun Jae explained that such information should not be leaked to avoid mass hysteria.
With new vital information, the question is how they can manage the production of the lunar water, given it can multiply endlessly.
