Blocking the windows in advance proved useful, as the sticky sound was exactly the aliens hitting the metal panels outside. Even players inside the carriage could hear sounds like mouths or suction cups turning on the metal panels, searching alive for gaps to enter the carriage.
The players didn't feel very pleasant at the moment; there's no doubt that they've been surrounded. Although they couldn't see exactly what those things outside looked like, they imagined them to be even stranger than the aliens seen before. They're all on top of the train, but their mouths were at the sides of the windows—species that look unrealistic usually result from severe genetic mutation and possess unexpected attack power.
Now, the windows were sealed, but they were still outside searching incessantly. Before long, heavy dropping sounds accompanied by the shattering of windows came from behind, and everyone suddenly realized: some carriages didn't include the transitional carriages in the sealing!
