Dual Purpose is a mission in Marvel's Spider-Man. Prior to the explosions in the And the Award Goes to... mission, Peter Parker was sure he saw Martin Li at the scene with the Inner Demons. Though he tries to convince Yuriko Watanabe of this, she demands he find evidence before she can do anything.
Mary Jane Watson calls him with a tip about Li and a recycling business he bought a controlling interest in. She also reveals what the arrested Inner Demons have said about Li – that he brings out the "negative" side of people so they do things they normally would not do.
Players proceed to take out the guards at the center with a mix of open fighting and stealth-webbing from above. When the door is reached, they then must discover where the junction box is located and use their Electric Web to short it out. Another circuit junction should be tripped in the same way, and then they gain access to the building. A few small fights later and a crawl through one of the vents, and players are in the room where the evidence is located.
Inside, Spider-Man finds a map that appears to target all of the campaign offices of Norman Osborn. Further evidence includes gadgets, explosives from the construction sites of Wilson Fisk and his weapons, and blueprints for truck bombs. He finds the address to Consolidated Shipping, and players then proceed to that area.
When players arrive at the address, it is obvious it is heavily guarded, with plenty of snipers. At this point the Trip Mine gadget is unlocked for use, as this part of the mission relies on stealth. The Mine only has a few charges, so players need to be careful where and when they use them. The snipers should also be dealt with as quickly and quietly as possible, as alerting one will typically alert them all, and then the fight can get tough.
Once in the office, Spider-Man finds another map, this one of all the Demon Bases throughout the city. Attacking these successfully will earn players Base Tokens. He finds additional evidence, then departs the office, only to be attacked by a member of the Inner Demons wielding two "negative" whips.
The easiest way to deal with the whip enemy and those like him is to use throwables, avoiding air combat. Webbing them does not seem to be very effective, though seems to work somewhat just after they attack with a whip. More Demons arrive.
Just as players succeed in taking out the Demons, Sable International arrives. Spider-Man does not know who they are, and Silver Sable arrives herself via helicopter. They manage to capture Spider-Man using trap gadgets, and it is only through Yuri's timely arrival that he is ordered free. Yuri lets him know that Osborn has hired Sable for protection.