Whenever he discovered a lone or isolated vampire entering or leaving, he would tail them, waiting for the right moment to strike.
A day later, he noticed a vampire taking advantage of the cover of darkness, riding in a black car to enter this "big factory."
At this time, there were still two days remaining until the fresh blood needed to be transported to the Bloodsucking Sect.
The vampires from the Bloodsucking Sect arrived a day early, presumably to inspect the goods, verify the quantity, and ensure that the royal nobles of the Alexander Empire had done their job correctly.
Lin Yifan felt the timing was finally right and kept his eyes peeled, monitoring the situation around the clock without even pausing to eat.
After over ten hours, he still gained nothing.
Once the group of vampires entered, they never came back out, seemingly planning to stay inside until the train embarked the next day.