Zayn was a 'blink' he was meant to kill Harry, Harry was an assassin and was meant to kill Zayn but they couldn't. Zayn suddenly had to go and comes back to where Harry works to see him again about 15 years later with a child after Harry demands to know what happened Zayn tells him. This talks about how Zayn and Harry fell in love and why Zayn had to go from Chapter Two, Chapter One happens about 15 years after they first meant. Please just read it should hopefully make sense thanks.