How can I get three aliens all at once?

There are much more than three in the harbor.

But you'd rather they didn't have their scary dogs with them.

Have you looked in the Inn's GUEST BOOK?

These names almost sound made up. Could they maybe be aliens?

And what's that about the chain of command?

Go upstairs to see the new guests.

Do you have the room keys? If not, come back after you find them.

Unlock all three doors.

You need to open the doors in the correct order, in other words follow the "chain of command."

According to the note in the guest book, the aliens match the status of the previous room occupants.

A General in room 1, a Sergeant in room 2, and a Major in room 3.

(SOLUTION FOLLOWS)

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Open the doors in the following order: 2-3-1.