D&D4 Wiki
Hidden blade
rogue utility 6

Prerequisite: Thievery trained

Effect: "You gain combat advantage for the next attack you make with an off-hand weapon before the end of your turn."[PHH1:MH2][HotFL:182]

Hidden blade is an encounter power available to rogues at 6th level.

It is an average choice, as the conditional combat advantage works for one attack but isn't target specific.[1]