When you wear it, clicking on it (or while in the air) will shoot a line to the closest object or structure. The grappling bowtie is the only way to reach the Rooftops and rescue the third spy. There...
first you have to jump and then while your at midair you aim where you want to go and the you click.
well you need to find the last place on the map and go forward then you go into the store and the guy in the black t-shirt for it
If a player loses Darklight, it can be retrieved by talking to Sir Prysin in Varrock Castle and paying him 1,000 coins.
Go to where you bought it and buy another cape and you'll get another hood.