What killed Lily Yu?

"I've seen it before?" you wondered. "Really?"

"Yeah, really. You've seen it before." Detective W asserted.

You looked at the corpse again and touched it. "It's cold..." you observed. Some wisps of vapor trailed from the closet frame.

'Cold...? Vapor...?' you thought. 'But how can it be cold and have steam at the same time? It's... weird...'

You remembered the fumes from the ice cream you ate earlier. "Ice cream? It's cold... wait... no way, it's impossible... liquid nitrogen?"

"Yes way," Detective W said. "The murder weapon was liquid nitrogen. No wonder Lei Hui didn't have enough liquid nitrogen for the ice cream. Remember what he said? He should have more than enough, but somehow, he didn't."

"Wait... I get why her skin feels cold now. But, why did the closet door explode, then? It doesn't make sense!"

"Yes, it does. When liquid nitrogen evaporates, it expands to nearly 700 times of its liquid volume. And there's six canisters here. That's enough to blast the door open."

Hua Xiu, who just got down from the stairs, covered her children's eyes. "No way... Lily? Lily died?"

Lei Hui just stood besides his wife, unsure of what to do. The rest of the guests started talking amongst themselves, discussing the killer's identity.

While Hua Xiu called the police, you and Detective W looked around the area for more clues. You sprawled on the ground, checking each tile with detail. You crawled to the dining room, looking underneath the dining table. A powder-like substance was found underneath a leg.

You scooped it in your hands, and sniffed it. "Boss, you have any idea what this is?" You then poured the white powder onto Detective W's palm.

"No clue," he admitted. "Could be sugar, salt, or anything. Best not to taste it." He then showed you what he found around the area.

Behind the closet, the wall had a streak of dark stains. There were several small, circular stains close to each other and the rest seemed wiped off. There were also some tiny droplets on the wooden floor.

Detective W then taped the area off with his trusty blue tape. "Don't let anyone near this area, okay? And tell Ha-Eun and Ha-joon to look for more clues in this mansion." he ordered you.

"If I can figure out why those stains are there... I could get a clearer picture..." Detective W muttered and stroked his chin. "It's time to ask some questions."

---------------------It's not over yet!--------------------