General objectives of the stage: Elimination of Dexter, depending on your previous actions, can run smoothly or can require a much of reflex.
Regardless of previously chosen path, you'll find yourself on the heliport, where you can find Blake Dexter and Victoria being kept by him. The situation can take two courses here. If Dexter has noticed you, you have to quickly shoot him.
A much better idea is approaching Dexter without alerting him. In such case you can defeat him in a melee fight, shoot him or use a garrote to kill him (screen above). Killing Dexter results in completing the nineteenth game mission and advancing to the final task.