Instructions
Fly the helicopter to the Pacific Northwest once Harold Mews adds the location to your computer. Follow Bigfoot after you've spotted him and make sure not to let him get out of your line of sight. Mews and Gretchen will contact you on the radio after Bigfoot makes his way back into his cave. Catch up to Gretchen by bumping into her helicopter with your own.
Leap over to Gretchen's copter from the top of your own and click on her gas tank. Release Bigfoot from his cage by jumping on top of it and applying the Gardening Shears. Your parachute will see the both of you to a safe landing.
Speak to Mews and listen to him tell you he lacks the finances to provide an appropriate environment for Bigfoot. By turning down his reward, you give him the resources to become Bigfoot's caretaker. Mews then gives you the Cryptids Island Medallion and 100 credits.