Bowl of Roses: A "whodunnit" murder riddle

Bowl of Roses

Shemira, a rich woman, hurries to the living room while shouting to her servant Nemora.

Shemira: Nemora! Nemora!!!!
Nemora: What is it, master?
Shemira: Where're the tissues?
Nemora: The new tissues I bought was in the kitchen, master.
Shemira: Then why are you standing in there?! Get it for me!

As her master shouted, Nemora ran into the kitchen to get the box of tissues. Her master caught a cold and currently suffering of clogged nose.

Nemora: Here's your tissues master.
Shemira: I will take a nice dip in my bathtub. Take those rose petals in the table and leave them at the bathroom door after you finish cleaning here. Understood?! * blows her nose*
Nemora: yes master.

After about half an hour, Shemira's friend Belinda arrives.

Belinda: Where's your master?
Nemora: She is in the bathroom ma'am. Please don't disturb her.
Belinda: Taking a beauty bath huh? That girl really doesn't want my ex-boyfriend to come back to me. Arghhh!

Belinda then walks heading for the stairs to the second floor where the bathroom was located.

In just less than a minute, Shemira's boyfriend Ulric arrive and asked Nemora too.
Ulric: Where is your master?
Nemora: She was taking a bath on the second floor. Please don't disturb her sir.
Ulric: It's fine, I'll just talk to her.

Ulric then walks heading for the stairs to the second floor.

After about half an hour, a scream was heard on the second floor. Nemora rushed up to the stairs.

Ulric: Nemora! Hurry! Call an ambulance!

Shemira was submerged in the water. Lifeless. While Ulric is kneeling by the tub, crying

Nemora checked her pulse.

Nemora: It's useless to call an ambulance now. She is dead. We better call the police * with a sad expression in her face*

Ulric then called the police.

The police arrived with Detective Brutus.

Brutus: What evidences did you gather?

Police officer Saveas: We have found traces of substance that can cause dizziness and sleepiness in the tissue sir. It is located near the tub and inside a box. The room was locked from the inside before the body was discovered, as stated by his boyfriend. We can deduce that someone put something in the tissue to make the victim sleepy and eventually drown on her own in the tub. I will now call the three suspects sir for their alibis.

Brutus: Shemira was murdered. Someone put a sleep-inducing substance in the tissues she had. Now Nemora please tell me your alibi. You are the one who gave the tissues.

Nemora: I didn't kill her! Yes, I gave her the tissues but she used it even before she goes to the bathroom. She must have fallen asleep earlier because she has a habit of reading magazines about beauty tips in her room before bathing if I am the murderer. Maybe someone managed to get into the bathroom and used the tissues to put him to sleep.

Brutus: hmmmmm... how about you? You are the victim's boyfriend and the one who discovered the body right?

Ulric: Yes, but I can't kill her!

Belinda: ohhh don't lie! You have the spare key to the bathroom. You can kill her!

Ulric: She was still alive when I knocked on her door for the first time. She tosses something into the door as a sign for me to leave. I even saw her hand reaching for the roses by the door when I am opening the guest room two rooms away from the bathroom. I have a spare key but I only used it when I knocked on her door for the second time and she doesn't respond to me when I called her outside the bathroom. I thought something bad may happen to her so I opened it. And now she is dead *cries*

Brutus: hmmmm... and you ma'am?

Belinda: I knocked on her door only once, officer. But she also didn't respond. So I went to her storage room for the painting she borrowed to me. Here's the painting officer if you don't believe me.

Belinda showed the painting. Brutus noticed a wet mark on the back of it.

Brutus: Ok ok. All of you stay here. Officer Saveas come with me, please.

Saveas: Why are you smiling sir? Don't tell me you solved it already?

Brutus smiled even more.

Who is the murderer?