In this chapter of our Marvel's Spider-Man Game Guide, you will find a walkthrough for the Hidden Agenda mission related with the main storyline. Peter decides to search Martin Li's office and look for evidence of his criminal activities.
Head to F.E.A.S.T. where Peter will talk to his aunt May. After the cutscene, you can walk around the hostel, talk to the residents, or help with cleaning. Your main goal is to reach Martin Li's office. The front door is closed - enter the ventilation shaft.
Jump into Martin's office. Go up to his desk, open the drawer and take the key out of the logbook. Now approach the picture on the wall and open the hidden mechanism. You must set the pattern to resemble yin and yang. The solution can be found in the picture above.
Get into a secret room and start your search. After you check all places, Peter falls into a trap - target both electrical boxes and shoot them to turn off the power. Then, use the manhole to move down. Go outside and you will meet Martin. After the cutscene, the mission will end. You will get a reward of 3000 XP.