Annabel's brilliant friend Charlie was a bit of a mad scientist. And although the first explosion he caused at Jerrard's lab in Norfolk had been a minor affair, this last one threatened to get him sacked.
Sam Jerrard refused to listen to reason. He resented Annabel's impassioned plea on Charlie's behalf and misinterpreted it, too, in more ways than one.
So Annabel stowed away in Sam's car to get him alone and have one last go at persuading him to change his mind. Then the chemical mix became truly volatile!