Uniform Stealing Board

Here is one season 4 episode 19

A woman assassin dressed as a driver kidnapped Mrs Hart to go to a function when they get to the function Mr Hart and max rescue Mrs hart, but the woman assassin escapes still as a driver. But she is there to kill her former boss who double crossed her next you see the assassin dressed in some woman's clothes she stolen at the function. Ready to kill her former boss.

https://www.dailymotion.com/video/x6lx6n0


where is the scene?

Think I found it. The female assassin who's wearing that driver disguise is seen wearing a completely new outfit at 28:25. Grim is right there's no scene before hand she just appears in a new outfit which means I guess its up to the viewers imagination as to whether or not she knocked out a party guest and stole her dress or just changed somewhere.