Mo Ruyue had tested this whistle in her space. It could emit a whistle sound with a special frequency, which could be sensed by the Bai family's specially reared whistle slaves.
"This is the safest method of communication. As long as we don't lose the sentry slave, no one will find out that someone is sending messages right under their noses."
After receiving the test results, Mo Ruyue had praised this contact post.
Although Mo Ruyue had gotten the contact post, she had rejected the post slave.
As a person who hid a huge secret, she was not used to letting a stranger follow by her side, especially a stranger who was loyal to another family.
Even if she had a very close relationship with this family, it would not do.
Other than Gu Ying, no one knew the true secret of this space.
Even Aunt Liu and her babies only knew that they would be in an unfamiliar environment and could move with Mo Ruyue.
