It's time for a flashback. You have to escape the GENTEK facility. Jump over the fence and then run towards the place marked on your map and radar. Ignore the helicopter chasing you right now.
Once you get to the spot, confront the enemy. Mercer will grab a taxi cab and your job is to lock on the helicopter and throw the car towards it.
Once the machine will fall down, climb the nearby skyscraper. You can do it by using the sprint button. Use the objects on the roof to eliminate enemy helicopters coming your way. Perform the throws while the machines are not moving - otherwise you might miss them.
Time for another flashback. Consume the guy who comes to you in the alley, watch the cut-scene and then move to marker on the map - Mercer's sister's apartment. Once you get there, climb up on a roof nearby and stand in the designated location.
It's time to use a disguise. Shapeshift into the soldier you've consumed recently and enter the apartment.
Reward: 5000 EP