At eight forty on Saturday morning, Frida found a rope hanging from the diving platform. It had far too many knots.
星期六早上八点四十，弗丽达发现跳台上垂着一根绳子，绳子上的结多得离谱。
She stood on the wet tiles of the rooftop pool and touched each knot with one finger. There were thirty-one of them, tied tight, and some were as big as plums. Behind her, the water looked grey and cloudy.
她站在屋顶泳池湿漉漉的瓷砖上，用一根手指挨个儿碰着每个结。一共有三十一个，系得很紧，有些大得像李子。她身后，池水看上去灰蒙蒙的，有些浑浊。
"Aarav, come and look at this," she called.
“阿拉夫，来看看这个，”她喊道。
Aarav came out of the changing room with a mop over his shoulder. He was sixteen, like Frida. He worked at the pool on weekends to save money for a new bike.
阿拉夫肩上扛着拖把，从更衣室里走出来。他和弗丽达一样，十六岁。他周末在泳池打工，想攒钱买一辆新自行车。
"That is not a normal rope," he said. "Who tied all those knots?"
“这可不是一根普通的绳子，”他说，“谁打了这么多结？”
"I think the manager did." Frida held up a piece of paper. "Read this. It was on the front desk."
“我想是经理。”弗丽达举起一张纸。“你读读这个。它在前台上。”
The note said, "Gone to collect the trophies. Back at ten thirty. Please start the water pump by nine thirty. The code for the pump box is on the rope."
便条上写着：“去取奖杯了。十点半回来。请在九点半前启动水泵。水泵箱的密码在绳子上。”
"On the rope?" Aarav read the note twice. "Why didn't he just write the code down?"
“在绳子上？”阿拉夫把便条读了两遍。“他为什么不直接把密码写下来？”
"Last week he did, on a sticky note. A little boy found it and pushed the emergency button." Frida looked at the big clock above the snack bar. "The whole pool stopped for an hour."
“上星期他写了，写在便利贴上。一个小男孩发现了，按了紧急按钮。”弗丽达看了看小吃店上方的大钟。“整个泳池停了一个小时。”
"So now the code is hidden." Aarav put down his mop. "How long do we have?"
“所以现在密码被藏起来了。”阿拉夫放下拖把。“我们还有多长时间？”
"Fifty minutes. The first swimmers come at half past ten. The water needs an hour of cleaning before they jump in."
“五十分钟。第一批游泳的人十点半到。水要净化一个小时，他们才能下水。”
"Then we need that code," Aarav said, and he started to pick at the nearest knot.
“那我们得找到密码，”阿拉夫说着，开始抠最近的那个结。
The knot was wet and hard. After three minutes, Aarav had only loosened it a little, and his fingers hurt.
结又湿又硬。过了三分钟，阿拉夫只弄松了一点点，手指也疼了。
"This will take all day," he said. "There are thirty more."
“这要花一整天，”他说，“还有三十个呢。”
"Maybe the manager hid a paper inside one of them," Frida said. "Keep going. I will try the next one."
“也许经理在其中一个结里藏了张纸条，”弗丽达说，“继续弄。我来试试下一个。”
They worked side by side for ten minutes. Aarav opened four knots, and Frida opened three. Inside them there was nothing at all, only damp, twisted cord.
他们并排干了十分钟。阿拉夫解开了四个结，弗丽达解开了三个。里面什么都没有，只有潮湿、扭在一起的绳子。
"Maybe we should cut the rope," Aarav said. "The scissors are in the first-aid room."
“也许我们该把绳子剪断，”阿拉夫说，“剪刀在急救室里。”
"If we cut it, we might destroy the clue." Frida wiped her hands on her shorts. "Let me check the box first."
“剪断的话，可能会毁掉线索。”弗丽达在短裤上擦了擦手。“让我先去看看那个箱子。”
The pump box stood in the corner of the roof, a grey metal cabinet with a heavy padlock. The lock had four number wheels. Above each wheel, somebody had stuck a tiny coloured dot. The first was blue, the second white, the third green, and the fourth yellow.
水泵箱立在屋顶的角落里，是一个灰色的金属柜，上着一把沉重的挂锁。锁上有四个数字转轮。每个转轮上方，都有人贴了一个小小的彩色圆点。第一个是蓝色，第二个是白色，第三个是绿色，第四个是黄色。
Frida stared at the dots for a long moment. Then she looked back across the roof at the rope, and her eyes opened wide.
弗丽达盯着那些圆点看了很久。然后她回头望向屋顶另一头的那根绳子，眼睛睁得大大的。
"Aarav! What colour is the rope?"
“阿拉夫！绳子是什么颜色的？”
"Grey, I think." He frowned. "No, wait. It is blue near the top."
“灰色吧，我想。”他皱起眉头。“不对，等等。靠上面的地方是蓝色的。”
They ran back to the platform together. Frida lifted the rope and walked her hands down it. The top part was blue. Further down it turned white, then green, and the last part was yellow.
他们一起跑回跳台。弗丽达提起绳子，双手顺着往下摸。上面一段是蓝色的。再往下变成了白色，然后是绿色，最后一段是黄色。
"It is four pieces of old lane rope, tied together," she said. "The manager never throws anything away. He has been saving these pieces for years."
“这是四段旧的泳道绳连在一起，”她说，“经理从来不扔东西。这些绳子他已经攒了好多年了。”
"And the dots on the lock have the same four colours." Aarav smiled for the first time that morning. "So we don't have to open any knots."
“锁上的圆点也是同样的四种颜色。”阿拉夫露出了今天早上的第一个笑容。“这么说我们不用解开任何一个结。”
"We only have to count them. Seven knots might mean the number seven on the first wheel."
“我们只需要数一数。有七个结，也许就代表第一个转轮上的数字是七。”
"That is a good guess, but we have to be careful," Aarav said. "If we make one mistake, the lock will not open."
“这个猜测不错，但我们得小心，”阿拉夫说，“只要错一个，锁就打不开。”
Frida checked the clock. It was nine fifteen. She counted the blue part first, touching each knot slowly. Aarav counted the white part, and then they swapped places to check each other's numbers.
弗丽达看了看钟，九点十五分。她先数蓝色的那一段，慢慢地碰着每一个结。阿拉夫数白色的那段，然后他们换过来，互相核对数字。
"Blue has seven," Frida said. "White has nine."
“蓝色有七个，”弗丽达说，“白色有九个。”
"Green has eight," said Aarav. "And yellow has six."
“绿色有八个，”阿拉夫说，“黄色有六个。”
They ran to the pump box and tried seven, nine, eight, six. The padlock did not move. Aarav pulled it hard, but it stayed shut.
他们跑到水泵箱前，试了七、九、八、六。挂锁纹丝不动。阿拉夫用力拉了拉，它还是锁着。
"We made a mistake," he said. "Think, Frida. What do we know for sure?"
“我们弄错了，”他说，“想想，弗丽达。我们能确定的是什么？”
"We know the total." She stopped. "There are thirty-one knots in all. I counted them at the beginning. But seven, nine, eight and six make only thirty."
“我们知道总数。”她停住了。“一共有三十一个结。我一开始数过。可是七、九、八、六加起来只有三十。”
"So one of our numbers is wrong, and we only lost one knot." Aarav looked at his watch. "It is nine twenty-one."
“所以有一个数错了，而且只少了一个结。”阿拉夫看了看手表。“九点二十一分。”
"Which part is the hardest to count?"
“哪一段最难数？”
"The yellow part. It is full of tiny knots, and the end of it is dirty from the floor."
“黄色那段。上面全是小结，末端又沾了地上的脏东西。”
They hurried back to the rope. This time Aarav closed his eyes and counted the yellow part with his fingertips. Halfway down, he stopped and made a small noise.
他们匆匆赶回绳子那儿。这回阿拉夫闭上眼睛，用指尖数黄色那一段。数到一半，他停住了，发出一声轻轻的惊叫。
"Frida, feel this. These two are tied right next to each other. Last time they felt like one big knot."
“弗丽达，摸摸这里。这两个紧挨着系在一起。上次摸起来像一个大结。”
Frida touched the place and nodded. "That is the missing one. Yellow has seven, not six."
弗丽达摸了摸那个位置，点点头。“少的就是它。黄色是七个，不是六个。”
The clock said nine twenty-six. They ran across the wet tiles to the pump box. Frida turned the wheels with shaking fingers: seven, nine, eight, seven.
钟上显示九点二十六分。他们跑过湿漉漉的瓷砖，奔向水泵箱。弗丽达用颤抖的手指拨动转轮：七、九、八、七。
The padlock opened with a loud click.
挂锁“咔哒”一声，开了。
Inside the cabinet there were two black switches and one big green button. A paper sign said, "Switches up. Then press." Aarav pushed both switches up, and Frida pressed the button with her whole hand.
柜子里有两个黑色的开关和一个大大的绿色按钮。一张纸牌子上写着：“开关向上，然后按下。”阿拉夫把两个开关都推了上去，弗丽达用整只手掌按下按钮。
For a second, nothing happened. Then a deep hum started under the floor. At the edge of the pool, the water began to move, slowly, towards the filter. Small bubbles rose up and popped.
有那么一秒钟，什么事也没发生。然后一阵低沉的嗡嗡声从地板下响了起来。池边的水开始缓缓地朝着过滤器流动。小气泡升起来，啵地破掉。
"Nine twenty-nine," Aarav said, and he dropped onto a plastic chair. "One minute to spare."
“九点二十九分，”阿拉夫说着，一屁股坐到塑料椅子上。“还剩一分钟。”
"The water will be clear by ten thirty." Frida laughed. "And the swimmers can come in."
“十点半之前，水就会变清了，”弗丽达笑着说，“游泳的人可以进来了。”
Aarav took out his phone. He had sent a message to the manager at nine ten, and there was still no answer. Now a new message arrived, and he read it aloud.
阿拉夫掏出手机。他九点十分给经理发过信息，一直没有回音。现在来了一条新消息，他大声念了出来。
"It says, 'Did you find the code? I tied the knots in the car park at midnight. It took me an hour.'"
“上面写着：‘找到密码了吗？这些结是我半夜在停车场系的，花了一个小时。’”
"An hour!" Frida shook her head. "He should have used fewer knots."
“一个小时！”弗丽达摇着头。“他应该少打几个结。”
"I agree. Thirty-one is a crazy number." Aarav grinned. "But the colours were clever."
“我同意。三十一个，真是个疯狂的数字。”阿拉夫咧嘴笑了。“不过那些颜色挺聪明的。”
Frida went to the front desk and found a pen. She turned the manager's note over and wrote in big letters, "Next time, please use fewer knots." Then she stuck the note on his office door.
弗丽达走到前台，找到一支笔。她把经理的便条翻过来，用大大的字写道：“下次请少打几个结。”然后把便条贴到了他办公室的门上。
