You might have heard that the first 48 hours are the most important when solving a crime as the missing persons are more likely to be found, evidence is still fresh and witnesses are likely to remember things.
Unfortunately, some crimes just don't get solved.
We've detailed some of the creepiest unsolved murders that still remain a mystery..
The Hinterkaifeck Murders
In the 1920 a farmer in Germany had noticed mysterious footprints in the snow around his house. There were also a number of strange things happening around the farm itself such as mysterious footsteps heard in the attic and a newspaper that no one in the household had bought. Later on, the keys to the house disappeared. What's weirder is a few months prior, the housekeeper had left the farm claiming the place was haunted.
The family suddenly went unseen for a couple of days. Their neighbours went round to check in on them, only to be met with the gruesome sight of the entire family including their newly hired housekeeper murdered. It appeared that most of the family had gone into the barn one by one and had been slaughtered with what is believed to have been a pickaxe. The housekeeper and the family's youngest son were killed in their beds, and more horrifying, the youngest daughter had actually survived for a few hours after the attack.
The maid who had also been killed was on her first day of the job. The previous maid had quit claiming she believed the farm to be haunted.
Despite tireless efforts by the police, they never found the culprit who carried out the heinous attack. To add an additional layer of mystery, whoever it was that committed the attached remained in the house after the murders. The neighbours reported seeing smoke coming from the chimney, and food had been eaten from the kitchen.
The Villisca Axe Murders
The Villisca Axe Murders occurred between the evening of 9th June 1912 and the early morning of 10th June 1912, in the town of Villisca, Iowa. The victims were six members of the Moore family and two house guests, who were found bludgeoned to death within the Moore residence.
at 7am on the 10th June, the Moores' neighbour became concerned after she noticed that the family had not come out to do their morning chores. She knocked on the door, and when nobody answered, she tried to open the door and discovered it was locked.
When police came to investigate, they found no sign of a break in and they found two spent cigarettes in the attic, which suggested that the killer or killers had patiently waited in the attic until the Moore family and their house guests were asleep.
Almost everyone was sharing a bed in the small house and what is strange is that none of the victims appeared to have woken up during the attack. All the mirrors in the house were also found to have been covered by sheets.
The Texarkana Moonlight Murders
Also known as The Phantom Killer, an unsolved case surrounding a ten-week killing spree in 1946 in Texarkana. The unidentified serial killer was reported to have attacked eight people within ten weeks, five of whom where killed, usually three weeks apart. The attacks happened on weekends between 22nd February 1946 and 3rd May 1946.
The town became stunned with fear and at dusk residents in the city heavily armed themselves and locked themselves indoors while police patrolled the streets looking for the killer.
The description of the attacker, given by one of the survivors, was a six foot tall man who wore a white mask over his face with holes cut out for his eyes and mouth.
To this day, he has never been caught.
The Mysterious Case of Elisa Lam
Twenty one year old student Elisa Lam was staying at the Hotel Cecil in LA when she went missing at the end of January and was found dead two weeks later in the hotel's water tank.
After her disappearance, security footage was released by the Los Angeles Police Department showing Elisa behaving very erratically in the hotel's lift.
Elisa was only found after guests at the hotel complained of black and awful tasting water which led staff to check the water tanks on the roof of the hotel.
What's strange is that in the security footage, Elisa is acting like she is hiding from someone in the lift (in which she pressed all the buttons and the doors refused to close) and she continually peeps around the lift doors to look for someone or something.
Also, in order for her to reach the roof she would have had to get past multiple locked doors, only accessible by hotel staff, and climb into the giant water tanks which were sealed.
In a weird coincidence, the tuberculosis test being used in the area near the hotel at the time of Elisa Lam's death was called LAM-ELISA.
The Sommerton Man
The body of an unidentified man was found on Somerton Beach in Adelaide, South Australia in November 1948.
What's creepy about this particular case is that The Somerton Man had no signs of violence or struggle on his body and the cause of his death was indeterminable. Despite being dressed in a suit, he had no ID on his persons, but police did find a piece of paper in his pocket that read "Tamam Shud", which is Persian for "It is ended / finished." The page was said to come from a rate book titled The Rubaiyat which was found only a few streets away. The book had a ciphered message that was only visible using UV light.
Speculation went around about how The Somerton Man met his end, but no one will ever really know.
The Zodiac Killer
The Zodiac Killer is one of the most notorious unsolved murder cases after Jack the Ripper. Over 2,500 people were interviewed in connection with the case but no one was ever held accountable. The Zodiac Killer was known to have killed at least five people between December 1968 and October 1969. The targets were both men and women. The Zodiac Killer claimed to have killed 37 people in total and used press coverage and letters to taunt the police investigating the case at the time. The letters contained cryptograms and codes, only one of which was ever solved, and it was from these that the Zodiac Killer got his nickname.
The Beaumont Children
On 26th January 1966, 9 year old Jane, 7 year old Arnna and 4 year old Grant Beaumont hopped on a bus to take a five minute ride from their home to Glenelg Beach in Adelaide, South Australia.
They never returned home and have been missing ever since.
Not much is known about the Beaumont children's movements that day. They were seen on the bus at 10:10am, and they bought pastries at around 11:45am but seem to have disappeared sometime in the afternoon.
Their exact movements is hazy, due partly to a postman's report who couldn't remember if he had seen the children at the beginning or the end of his route.
The children were reportedly seen by several people in the company of a blonde haired man wearing blue swimming trunks. However, who he might have been and whether he had anything to do with the children's disappearance has never been determined.
Serial Killer Season starts Monday 13th June from 9pm