The burglar alarm went off just before 4 am , which was odd because it was n't set . Turned out the indoor alarm was sounding , but not the outdoor one . I rang the alarm company and the engineer suggested a couple of things to try out , which made no difference , so he said he would come out , although it would take him about 45 mins . A few minutes later , about 20 mins after it first went off , it stopped .
Question: Why was the narrator up at such a tough hour ?
The answer to the above question:


The internal alarm went off .