"Alright! You have a criminal record, tell me, did you kill the old woman?" Gao Mingqiang immediately cuffed the bald man.
"I didn't! I admit I've broken the law before, but I wouldn't like someone that old!" the bald man struggled to retort.
"Gao Mingqiang, calm down, he didn't handle any playing cards!"
Hearing about the playing cards, the bald man reacted with curiosity. "What playing cards? What's going on? How did the old woman die?"
"You don't need to know that. I believe you didn't kill anyone, but you have to be handed over to our colleagues!"
I handed him over to another officer, then patted Gao Mingqiang and said, "Don't be impatient, let's go ask others!"
"Why do you think he's not the murderer?"
"I'm investigating the matter of the playing cards. The killer handled a box of cards, and their fingerprints were on it. He wouldn't dare throw it away, or it would be hard to clear his name if we found it. I just checked the trash can and found a few discarded playing cards: the King of Spades and the Queen of Hearts."
"Were there any fingerprints on them?"
"There was some blood. It's estimated that the killer accidentally dropped them into the trash can without noticing. Otherwise, he would have picked them up and kept them. The trash can was a bit far from the old woman's seat, so I suspect someone switched them."
"You're very observant. Let's go!"
We went to the other tourists' lounge, but after asking several people, we found nothing. Then Liu Yuning and Xiao Yuande arrived. I asked them if they had found anything, and both shook their heads.
Puzzled, I wondered if the killer had already escaped in the chaos. But I remembered that the cruise ship's passenger list had been checked, and everyone was accounted for.
I returned to the vicinity of the trash can and shone a black light on it. I found a handprint, likely left unintentionally by the killer during the switch.
Seeing this, Liu Yuning said, "Why don't we compare this handprint with everyone on the ship?"
"Heh, that would take too much time, and the ship is leaving in less than an hour. We don't have time."
We had spent a long time asking questions and had wasted so much time that we didn't even have time to eat.
Then Gao Mingqiang asked curiously, "I just heard that the murder weapon was playing cards? What's that about?"
I picked up a playing card in front of him, held it up high, found an apple on a table, and sliced it in half with the card at top speed!
Seeing this, Xiao Yuande explained, "This is similar to throwing steamed buns off a train. The momentum of the steamed bun is p=mv. According to the impulse-momentum theorem, Ft = Δp = mvf = mv/t, where v is the speed of the train. So, even though the mass m of the steamed bun is small, its velocity v is very large, thus its momentum p is large. Also, because the bun's velocity v is very high, the impact time t with a person is very short, resulting in a large interaction force, which can kill someone."
"Exactly, that's what I meant!"
"I thought Uncle only had brute strength, I didn't expect his brain to be so sharp!" He Xin said in surprise.
I also thought that only He Xin would understand such theories.
"You flatter me. I actually enjoy reading quite a bit," Xiao Yuande replied calmly, appearing quite modest.
Looking at him, I became even more convinced that recruiting him for our team was a good idea.
We all went back to the lounge to screen the tourists one by one. After leaving the cruise ship, I lingered around the pier. He Xin followed me, not understanding what I was doing. "Dad, aren't you going to check with them?"
"There's no time. Let's go eat first!"
"What? No time and we're going to eat?"
He Xin looked at me in surprise, but I had already entered a Western restaurant, so she followed me.
She was probably hungry too. We both had a Western meal. During the meal, He Xin kept looking at me, worried that the case wouldn't be solved. But I ate my steak with ease.
When we came out, we had finished our meal. Liu Yuning saw us and was annoyed. "We're all busy and haven't had time to eat, and you two are here having a Western meal!"
"Don't worry, Captain Liu. I've already thought of a way!" I said.
"Oh? What other way do you have? We have at most 10 minutes left, and this case might be over for us!"
"Let them go back on the ship. Afterward, search the lounge. Those playing cards are suspicious!"
Upon hearing this, Liu Yuning immediately turned and left. I knew she thought some clue would be found in the rooms, but I didn't elaborate. I walked towards the cruise ship, where tourists were gradually boarding. I stood by the security check, observing closely.
Several times, people had metal items detected, and the machines beeped. The security personnel stopped them, but they only found copper coins or metal decorations.
However, as a girl approached the security scanner, she hesitated, constantly trying to switch positions with people in front of her, her hands clenched tightly. I immediately noticed something was wrong and glanced at Xiao Yuande.
As if signaled, he acted on his own. His movement was as swift as a fierce tiger, pinning the girl to the ground!
"What are you doing? Let go of me!" The girl struggled fiercely on the ground, but under Xiao Yuande's restraint, she was like a little rabbit, unable to resist.
I walked over to her. Gao Mingqiang and several officers arrived. Everyone was confused, but I suddenly said, "The killer is her!"
"What?" Everyone was stunned, not understanding what I meant. I quickly pulled the girl up and brought a handheld scanner close to her pocket!
*Beep!*
The machine made a sound. I directly pulled a box of playing cards from her pocket!
These cards were different from ordinary ones; they had gilded edges, very similar to the ones I found in the trash can earlier. The security scanner has a metal detection function, so it reacted to these cards. I hadn't noticed the gilded edges at first, nor had I thought of using the scanner against her. I thought of it while eating Western food.
But I hadn't deliberately asked the officers to guard here and had sent Liu Yuning away. The girl must have thought the police had given up since there weren't many officers around.
Who knew that at this moment, I would suddenly act? I understood that not many officers were needed; just Xiao Yuande was enough.
This is why I found the killer.
Of course, to prove she was the killer, a series of comparisons would be needed. I picked up her hand, observed it, and then looked at her reaction, immediately saying, "Confess, won't you? You're the one who switched them in the trash can!"