The ceiling consisted of large rectangular panels set in a framework of metal strips； and the corner of the panel above the picture had lifted slightly。
〃I saw that；〃 Roger said； 〃and I thought the others might be like it； so I lifted 'em； and they're all loose。 They just lift up。 Me and this boy tried it one night in our dormitory； before they took him away。 There's a space up there and you can crawl inside 。 。 。 。〃
〃How far can you crawl in the ceiling？〃
〃I dunno。 We just went in a little way。 We reckoned when it was time we could hide up there； but they'd probably find us。〃
Lyra saw it not as a hiding place but as a highway。 It was the best thing she'd heard since she'd arrived。 But before they could talk any more； a doctor banged on a table with a spoon and began to speak。
〃Listen； children；〃 he said。 〃Listen carefully。 Every so often we have to have a fire drill。 It's very important that we all get dressed properly and make our way outside without any panic。 So we're going to have a practice fire drill this afternoon。 When the bell； rings you must stop whatever you're doing and do what the nearest grownup says。 Remember where they take you。 That's the place you must go to if there's a real fire。〃
Well； thought Lyra； there's an idea。
During the first part of the afternoon； Lyra and four other girls were tested for Dust。 The doctors didn't say that was what they were doing； but it was easy to guess。 They were taken one by one to a laboratory； and of course this made them all very frightened； how cruel it would be； Lyra thought； if she perished without striking a blow at them！ But they were not going to do that operation just yet； it seemed。
〃We want to make some measurements；〃 the doctor explained。 It was hard to tell the difference between these people： all the men looked similar in their white coats and with their clipboards and pencils； and the women resembled one another too； the uniforms and their strange bland calm manner making them all look like sisters。
〃I was measured yesterday；〃 Lyra said。
〃Ah； we're making different measurements today。 Stand on the metal plate…oh； slip your shoes off first。 Hold your daemon； if you like。 Look forward； that's it； stare at the little green light。 Good girl 。 。 。 〃
Something flashed。 The doctor made her face the other way and then to left and right； and each time something clicked and flashed。
〃That's fine。 Now e over to this machine and put your hand into the tube。 Nothing to harm you； I promise。 Straighten your fingers。 That's it。〃
〃What are you measuring？〃 she said。 〃Is it Dust？〃
〃Who told you about Dust？〃
〃One of the other girls； I don't know her name。 She said we was all over Dust。 I en't dusty； at least I don't think I am。 I had a shower yesterday。〃
〃Ah； it's a different sort of dust。 You can't see it with your ordinary eyesight。 It's a special dust。 Now clench your fist… that's right。 Good。 Now if you feel around in there； you'll find a sort of handle thing…got that？ Take hold of that； there's a good girl。 Now can you put your other hand over this way… rest it on this brass globe。 Good。 Fine。 Now you'll feel a slight tingling； nothing to worry about； it's just a slight anbaric current 。 。 。 。〃
Pantalaimon； in his most tense and wary wildcat form； prowled with lightning…eyed suspicion around the apparatus； continually returning to rub himself against Lyra。
She was sure by now that they weren't going to perform the operation on her yet； and sure too that her disguise as Lizzie Brooks was secure； so she risked a question。
〃Why do you cut people's daemons away？〃
〃What？ Who's been talking to you about that？〃
〃This girl； I dunno her name。 She said you cut people's daemons away。〃
〃Nonsense 。 。 。 〃
He was agitated； though。 She went on：
'〃Cause you take people out one by one and they never e back。 And some people reckon you just kill 'em； and other people say different； and this girl told me you cut…〃
〃It's not true at all。 When we take children out； it's because it's time for them to move on to another place。 They're growing up。 I'm afraid your friend is alarming herself。 Nothing of the sort！ Don't even think about it。 Who is your friend？〃
〃I only e here yesterday； I don't know anyone's name。〃
〃What does she look like？〃
〃I forget。 I think she had sort of brown hair 。 。 。 light brown； maybe 。 。 。 ！ dunno。〃
The doctor went to speak quietly to the nurse。 As the two of them conferred； Lyra watched their daemons。 This nurse's was a pretty bird； just as neat and incurious as Sister Clara's dog； and the doctor's was a large heavy moth。 Neither moved。 They were awake； for the bird's eyes were bright and the moth's feelers waved languidly； but they weren't animated； as she would have expected them to be。 Perhaps they weren't really anxious or curious at all。
Presently the doctor came back and they went on with the examination； weighing her and Pantalaimon separately； looking at her from behind a special screen； measuring her heartbeat； placing her under a little nozzle that hissed and gave off a smell like fresh air。
In the middle of one of the tests； a loud bell began to ring and kept ringing。
〃The fire alarm；〃 said the doctor； sighing。 〃Very well。 Lizzie； follow Sister Betty。〃
〃But all their outdoor clothes are down in the dormitory building； Doctor。 She can't go outside like this。 Should we go there first； do you think？〃
He was annoyed at having his experiments interrupted； and snapped his fingers in irritation。
〃I suppose this is just the sort of thing the practice is meant to show up；〃 he said。 〃What a nuisance。〃
〃When I came yesterday；〃 Lyra said helpfully； 〃Sister Clara put my other clothes in a cupboard in that first room where she looked at me。 The one next door。 I could wear them。〃
〃Good idea！〃 said the nurse。 〃Quick； then。〃
With a secret glee； Lyra hurried there behind the nurse and retrieved her proper furs and leggings and boots； and pulled them on quickly while the nurse dressed herself in coal silk。
Then they hurried out。 In the wide arena in front of the main group of buildings； a hundred or so people； adults and children； were milling about： some in excitement； some in irritation； many just bewildered。
〃See？〃 one adult was saying。 〃It's worth doing this to find out what chaos we'd be in with a real fire。〃
Someone was blowing a whistle and waving his arms； but no one was taking much notice。 Lyra saw Roger and beckoned。 Roger tugged Billy Costa's arm and soon all three of them were together in a maelstrom of running children。
〃No one'll notice if we take a look around；〃 said Lyra。 〃It'll take 'em ages to count everyone； and we can say we just followed someone else and got lost。〃
They waited till most of the grownups were looking the other way； and then Lyra scooped up some snow and rammed it into a loose powdery snowball； and hurled it at random into the crowd。 In a moment all the children were doing it； and the air was full of flying snow。 Screams of laughter covered pletely the shouts of the adults trying to regain control； and then the three children were around the corner and out of sight。
The snow was so thick that they couldn't move quickly； but it didn't seem to matter； no one was following。 Lyra and the others scrambled over the curved roof of one of the tunnels； and found themselves in a strange moonscape of regular hummocks and hollows； all swathed in white under the black sky and lit by reflections from the lights around the arena。
〃What we looking for？〃 said Billy。
〃Dunno。 Just looking；〃 said Lyra； and led the way to a squat； square building a little apart from the rest； with a low…powered anbaric light at the corner。
The hubbub from behind was as loud as ever； but more distant。 Clearly the children were making the most of their freedom； and Lyra hoped they'd keep it up for as long as they could。 She moved around the edge of the square building； looking for a window。 The roof was only seven feet or so off the ground； and unlike the other buildings； it had no roofed tunnel to connect it with the rest of the station。
There was no win