I killer vanno in pensione?

Why should an old man who has the delicacy of waiting every morning for his wife to wake up with a rose be the recipient of a parcel bomb? For Julia and Lieutenant Webb, engaged in the investigation into the explosion that took the life of Lucy Bernstein and the disappearance of Frank D'Angelo, her husband, things get complicated: the key to everything is in the missing man's past, but it feels like hunting a ghost, because Frank D'Angelo's life is, apparently, one of those too colorless to leave a trace...