Dance With Someone In A Mask Day!
Your face should not be hidden because it's so pretty and we wanna keep looking at it. But your dance partner should have her face completely concealed by a mask. Preferably, a feathery mask or something with sparkles. Or a rubber Darth Maul mask.
Most importantly is you should not know the identity of your dance partner, but you should ask a string of seemingly innocuous questions like Is Madrid always this hot? and Was that mask expensive? The questions should continue until your dance partner offers an answer that makes you pull away and try to make out her eyes through the eyeholes to see if you know her after all. The answer will be something like My best friend in the world used to dance here until she died on Christmas morning in 2003 (the day your wife died), or The man who taught me to dance was named Leland Huntington (the man who killed your dead wife).
Not long after you realize who your dance partner really is, she'll be shot in the back and will fall dead into your arms. You'll drop her to the dance floor and race out the door to follow the newfound trail to your wife's killer.
Happy Dance With Someone In A Mask Day