Lawless: Brett. Another case over. Funny how going so far away makes you think about things close to home.Tilley: Clare. What happens now? She doesn't know where it's all heading.The Case: Lawless & Tilley are flying into Heathrow when disaster almost strikes. Fluke accident or deadly sabotage? It's only when the threats start that the police know what they're up against. Thousands of lives are at stake, from an invisible weapon. Taking to the skies has never been so dangerous. After all, what goes up, must come down -- one way or another...