what incident does Anne describe as "the scare" ?

"The scare" involved a carpenter coming to fill the fire extinguishers in the office. The Franks were unaware that he was coming and terrified they'd been discovered.

My hand's still shaking, though it's been two hours since we had the scare. I should explain that there are five fire extinguishers in the building. The office staff stupidly forgot to warn us that the carpenter, or whatever he's called, was coming to fill the extinguishers. As a result, we didn't bother to be quiet until I heard the sound of hammering on the landing (across from the bookcase). I immediately assumed it was the carpenter and went to warn Bep, who was eating lunch, that she couldn't go back downstairs. Father and I stationed ourselves at the door so we could hear when the man had left. After working for about fifteen minutes, he laid his hammer and some other tools on our bookcase (or so we thought!) and banged on our door. We turned white with fear. Had he heard something after all and now wanted to check out this mysterious-looking bookcase? It seemed so, since he kept knocking, pulling, pushing and jerking on it. I was so scared I nearly fainted at the thought of this total stranger managing to discover our wonderful hiding place. Just when I thought my days were numbered, we heard Mr. Kleiman's voice saying, "Open up, it's me."