Kidnap lets you seize an enemy and use him as cover to walk into guarded areas. You earn it by completing your first Bounty Hunt rather than with skill points.
Kidnap sits at position 7 of 19 in the Stealth tree. Kidnap costs no skill points. You need reward for the first Bounty Hunt before you can buy it. Jacob and Evie each have their own skill tree, so you buy Kidnap once for each twin.
Air Assassination
Drop onto a target from above and kill him in a high-profile strike.
Assassin Steps
Greatly reduces fall damage, silences your landings and makes your movement much quieter.
Chameleon
In Sneak Mode, Evie becomes invisible while standing still; only enemies very close by can spot her.
Double Assassination
Kill two nearby unaware enemies at the same time.