新概念英语mp3听力下载第二册lesson 92

First listen and then answer the question.
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.