The episode opened with a small plane crashing in the ocean, when the body is recovered it is found to be an I.C.E. Agent, Monica Jensen and was dead before the plane even took off.
Jensen’s supervisor Jeff Morrison asked McGarrett and Five-O to help him find her killer. The team started by trying to find her daily journal called “red book”. When they went to her house they found it had been broken into and pages torn from the book. Danny decided to take her dog with them to make sure it got someplace safe.
From the items they found in Jensen’s house the trail lead to a smoke shop that sold medical marijuana to patients with prescription cards, and also to those without. Five-O was able to tie one of the customers at the smoke shop to a fingerprint on the red book. When he was arrested he told them the same information he had given Jensen.
The information led to a poaching ring where everything from parrots to puffer fishes was being sold on the black market. The team found out the man most likely in charge was Dr. Yang, when they went to Yang’s office he had been taken.
The team was able to determine that one of Dr. Yang’s patients who was also a customer at the smoke shop named Liam, had taken him and had killed Jensen because she was trying to stop the poaching and he thought Yang was curing him of cancer.