Detective（偵探） Paul pays a visit（拜訪） to his best friend， Mr Brain. Mr Brain is a great scientist. He studies（研究） desert（沙漠） plants（植物） and animals. He and his helpers（助手） are working in the Sahara Desert（撒哈拉大沙漠）. Mr Brain found a new kind of cactus（仙人掌）. He is going to take it to his lab（實(shí)驗(yàn)室）. But last night， someone stole（偷） his cactus from his tent（帳篷）. His three helpers are the only suspects（犯罪嫌疑人）.

There was strong wind last night. It’s cold in the Sahara Desert at night. So I had to fix（修理） my tent.

A few fireflies（螢火蟲(chóng)） flew into my tent last night. I tried to catch them. But I failed（沒(méi)抓到）. Then I went to bed.

I prepared（準(zhǔn)備） my camera last night. I wanted to take pictures of camels（駱駝） the next day. Then I went to bed.

Can you help Detective Paul find who stole the cactus？