Asking for Trouble

Why did the policeman ask the writer to come to the police station?     It must have been about two in the morning when I returned home. I tried to wake up my wife by ringing the doorbell, but she was fast asleep, so I got a ladder from the shed in the garden, put it against the wall, and began climbing towards the bedroom window. I was almost there when a sarcastic voice below said, 'I don't think the windows need cleaning at this time of the night.' I looked down and nearly fell off the ladder when I saw a policeman. I immediately regretted answering in the way I did, but I said, 'I enjoy cleaning windows at night.'
    'So do I,' answered the policeman in the same tone. 'Excuse my interrupting you. I hate to interrupt a man when he's busy working, but would you mind coming with me to the station?'
    'Well, I'd prefer to stay here,' I said. 'You see. I've forgotten my key.'
    'Your what?' he called.
    'My key,' I shouted.
   Fortunately, the shouting woke up my wife who opened the window just as the policeman had started to climb towards me.