Step 1: Starting the Quest
Speak to Sir Tiffy Cashien
Speak to Matthias

Speak to Sir Tiffy who will tell you about reports of pest sightings south of Falador. He will ask you to investigate the Void Knight Outpost to see if there is a chance a pest could have gotten past their watchful eye. Head to the Outpost and speak to Commodore Matthias, located on the eastern part of the island. He will allow you to interview citizens to see if they know anything and will send you to speak to Captain Tyr.

Step 2: Suspect Interviews
Speak to Tyr.
Interview the 9 people.
Confront Jessika.

Captain Tyr will send you to interview 9 people, all located on the eastern half of the island. Once you've spoken to all of them, talk to Tyr again. He will suggest you review what you've learned and confront the person you believe responsible. Speak to Jessika, who will deny it but mention that she was "freeing" them. Report her to Tyr, who will sent you to Commodore Matthias.

Matthias will perform his own interview of Jessika, but he still feels she is holding back. He will enlist you to take a potion to enter her mind to figure out what really happened. Once inside her mind, there will be a small slider puzzle that needs solving. Use the outside edges of the pieces as a guide to where each should go. When you complete the puzzle, you will hear Jessika saying that she released the pest.

Matthias will sentence her to house arrest and will commission a hunting party to find the pest. He will send you back to Sir Tiffy to update him on the recent events.

Step 1: Hunting Party Problems
Enter Korasi's memory.

Speak to Sir Tiffy, and he will agree to lend the aid of the Temple Knights. You will both head to Port Sarim to find Commander Korasi alone in a dazed state. Sir Tiffy will have her transported to Temple Knights HQ. Bank all of your items and speak to Sir Tiffy back in Falador to head to HQ.

Korasi will not be able to remember what happened. To discover her locked memories, she will give you another dose of potion to allow you to enter her mind. Speak to the toll booth, who will inform you that you have to complete a series of challenges to unscramble Korasi's memory.

Step 2: Mental Stimulations
Get everyone across the bridge.
Unscramble the memory.
Talk to Tyr.

The first task is to get yourself and the three Knights across the bridge. Each of you has a special weight, and each time someone crosses the bridge, the weight is added up; it can not exceed 15. Whenever someone crosses, they must have the sword. Up to two people can cross at a time (the weight applied is the heaviest of the two). To get everyone across, cross with Bernard, then return back. Send Ami and Dianna across. Send Bernard back, and finally cross over with him.

The second task involves listening to each of the knights and assigning them to a spot on the ship based on what they say. Matthias was at the helm, thinking about Jessika, and saw clouds. Korasi was in the hold, thinking about a promotion, and saw the pest. Diana was on the deck, thinking about fighting, and saw a seagull. Bernard was in the crow's nest, thinking about lunch, and saw seaweed. Ami was in the rigging, thinking about her sister, and saw a shark.

The ship was then attacked by pests and a mysterious magician and everyone except Korasi dies. Report your findings to Sir Tiffy in the Temple Knights HQ, and he will send you to inform Tyr of the recent events to complete the quest.