Seems to be out of order, an extra episode, or an OVA.
After the delivery girls tell a ghost story to the other children, an abandoned fleet of ships shows up on the radar. The girls sneak onto the boat that goes to check the fleet. Ridget has a flashback concerning the ghost fleet and an encounter seven years ago. After the flashback, the Gargantian crew figures out why the fleet was abandoned and returns to their ships.
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