# Help! I'm dying!

You are woken up to hearing your neighbour shouting - "HELP! HELP! I'M DYING!"

You jump to your feet and run out into the street and see a man run away from your neighbours house, but he is too far away for you to catch up with him, and he is wearing a mask. You decide to investigate the house, as you are an ex-policeman. You use your spare keys to go inside the house and see the body on the floor, dead. You also see a bit of paper sticking out of his pocket. You pick it up. It reads:

If you are reading this I am dead, but I believe I know who killed me. The answer is encrypted below.

eUXODGaaSDW8WURaLHaNWvjP2YNVJQWMSEdOWVQMSPdM9GaMJVjA6VQMJdRNWOhi7DcCATbiKRW

Damn it. Your neighbour loved cryptography. Oh well, you may as well have a go, you suppose. Then you notice something else sticking out of his pocket. Another bit of paper:

I've always had an extensive love of doughnut

What relation to him was the person that committed the murder?

NOTE: The reason of the puzzle being tagged "riddle" will be revealed later...

Hint 1:

Only two words on the second bit of paper are important.

Hint 2:

The two important words are "extensive" and "doughnut".

Hint 3:

CodeNewbie has guessed (correctly) that it has something to do with a Vigenere Cipher. However, only one word is the Vigenere Cipher key. The other is something else...

• DOUBT : when the victim is active enough to shout an awkward sentence like "HELP! HELP! A MEMBER OF MY FAMILY IS KILLING ME!" , why did he not simply scream "HELP! HELP! My {Brother/Sister/Uncle/Aunt} IS KILLING ME!" ? Why he can not reveal the name of the killer in his screams ? SUGGESTION : I would probably change his screams to "HELP! HELP! I AM DYING!" , and the paper clues will mention that a "family member" is trying to kill him. – Prem Jun 28 '15 at 10:27
• Thought: Donuts could mean a circle or torus. It's odd that it's singular and not plural. – Engineer Toast Jun 28 '15 at 13:25
• If he had enough time to write that message, then he must have known in advance that someone was going to kill him. In that time, couldn't he have called the police, gotten something to defend hinself, etc? – mmking Jun 28 '15 at 15:43
• @Kslkgh: Are the two words key to a vigenere cypher? – CodeNewbie Jun 28 '15 at 18:52
• But how can the numbers fit into a Vigenere cipher? – Rand al'Thor Jun 29 '15 at 6:21

The murderer is

The neighbour's son.

The message is encrypted using

an Extended Vigenere Square, which includes the characters A-Z, a-z, 0-9, and a space.

The decryption key, as mentioned by the hints, is

doughnut

Brothers and sisters I have none, but the murderer's father is my father's son.

This means that

the murderer's father is the victim, and thus it is the victim's son or daughter that killed him. Based on the clue about a masked man running from the house, I'm going to go with "son." Hopefully he has only one, or the case could be tied up for a while in court... :)

Being given that words "extensive" and "doughnut" are important to solving this I collected every letter contained within those two words. This gave me this:

eUXODGSDUHNvNVSEdOVSdGVVdNOhiDTi

I'm not 100% sure, but I thing the killer's relation is sister, because from that string you can almost get an anagram sister. From the cipher text you can get SisTE. Because you also said the singular doughnut has a meaning I think this is it. You meant the last letter was missing for security from being able to determine anagram too fast.

• Sorry, but no. There is a riddle involved. – user9377 Jun 28 '15 at 17:40

The murderer is

one of his dad's other sons by a different mother. The victim does not recognize him as a brother. (Brothers and sisters I have none, but the murderer's father is my father's son.)

Reasoning:

--------same father-------
|                                    |
male murderer     male victim (no siblings)

(apologies if the diagram above isn't formatted well on your screen)

Alternative: