With Greg Berlanti producing or supervising so many of CW’s DC Comics series and spinoffs at the moment, someone had the bright idea – or, at least, the cross-promotional cash-in concept – of connecting all the series into a same-week, every-show story. So there are four stops on the CW superhero route to complete this particular week’s story line – starting tonight with and on Supergirl. Tomorrow, the story continues on The Flash, then moves to Wednesday on Arrow, and concludes Thursday on DC’s Legends of Tomorrow.