Like all of the Silver Sphere Novellas, “Return of the Visitor” opens with a life-threatening event. The sixth book in the series finds Amy and Jacob Casell joined by their alien and android friends, attempting to evade a swarm of supersonic fighter jets determined to blow their Starship out of the sky unless the crew can identify themselves adequately.   The situation is grimly ironic because Silenna, an extraterrestrial from a survivor colony called New Aneleya, is returnin