We used to sit around the dinner table and plan how we'd rob and bank, and where we'd hide out (under the greenhouse) in town to wait for the dragnet to drop. Could we hide food there, would it keep, when would we go out for air, etc.
Several years ago, while I was on holiday on a cruise, I was trying to put together a detective story (family challenge: everybody was going to write a story over the course of the holiday. Mr Chick and the Younger Chick completed theirs; the Elder Chick and I bombed out). Nowadays when you get off or on a cruise ship, you go through security and present your photo-ID card, which is also your room key. The card is scanned, and if people are late, the crew members know precisely who they're looking for.
I reckoned that I had worked out a way to bypass security (on a one off basis suitable for a detective novel, I hasten to add; any of you involved in national security needn't come looking...) but I wanted to know what actually happens on a cruise if somebody disembarks on a port visit and doesn't come back. I'd been thinking about my plot on and off all day, so when the Entertainments Manager came round to chat with everybody, my mouth ran slightly ahead of my brain. As he shook my hand, I said brightly, 'now you're just the person I need to talk to: I'm going to do a murder and I need your help.'
The poor Entertainments Manager was so completely flummoxed that he actually forgot to let go of my hand and his expression was priceless. Apparently he'd never had a passenger ask him that before, and he developed a tendency to walk away hurriedly and hide behind doors when he saw me again, possibly in case I landed him with disposing of the body.
I still think my plot device would have worked, though.