Sometimes, especially on laptops with only one input, you have software options to select microphone-in or line-in. You want line-in.
BTW, I have occasionally used the "sox" (Sound eXchange) command line tools on Linux (though there are apparently Windows and Mac versions as well) to record overnight (rec -c 1 -r 8000 scanner.flac silence 1 1 .4 -1 1 .4). I set the options to only record when there is activity. On playback, I use the options to speed-up the playback (play scanner.flac tempo 1.5) while keeping the pitch the same so I can listen to an hour of recording in 40 minutes. I've only tried this a few times for fun but when I did, I could often listen to the whole night's activity on my drive to work.