Thought #30. The killer who was never caught 1/2.

Friday, 21st of December, 2011. 7:00 a.m. in the morning. The news bulletin opens with the 10th death in a row. "London Metropolitan police are conducting an investigation after the body of a middle-aged woman was found fully clothed, lying prone on the ground of Walthamstow Central Station. At first, constable B.I., the first police officer arriving at the crime scene, speculated about the possibility of a natural death. She soon changed her mind after seeing the sheer terror in the woman's motionless face."

Paul looks at his kettle. It definitely needs descaling. The sound of boiling water muffles the radio receiver, making the news bulletin unintelligible. The toaster is on. He is about to breakfast on tea and toasts, as usual. Suddenly, his mobile phone rings. "What the hell?", he murmurs. He is chief in command for the special operation launched on account of the series of killings that have been taking place recently. He warned the team not to bother him unless a new corpse was found. "It cannot be the case, not again", he tells himself.

- "Inspector May speaking", Paul answers reluctantly.
- "It's me, Beth. Sir, following the protocol, the area has been cordoned off. The mayor is coming and has requested your presence. Walthamstow Central Station, right at the entrance.", by her hurried voice's tone and the location of the body, Paul knows full well that it is going to be a long day.
- "I'm on the way. Don't talk to the media. Don't talk to anyone!"
- "Yes, sir.", they both hung up in unison.

7:30 a.m. Paul arrives at the surroundings of Walthamstow Central Station and a noisy flock of curious people are already trying to poke their nose into the investigation. From his position, Paul can see Beth accounting to the major. He jumps to his feet and approaches the scene, clawing his way amongst the crowd.

- "Good Morning, mayor Palmer", Paul utters with a serious countenance.
- "Good Morning, inspector", Mr. Palmer says while gesturing to Beth to recapitulate the facts.
- "Inspector, all the officers are completely baffled by this murder. We couldn't have predicted this twist in the case. We managed to foresee the station but the assassination was expected on Sunday 23rd.", Beth pointed out.
- "Well, it doesn't make any difference, we're going to arrest the killer at any cost. Mayor, as you may've been informed, the first body was found in Elephant & Castle Station while I was holding a dinner to celebrate my retirement. I had to put off that dinner for a while. I promised to stay in command until the case is solved and I'll keep my promise. It's all I can tell you at this moment."
- "I understand. Keep me informed. Officer, inspector", mayor Palmer says as he beckons his bodyguard. He leaves the scene jostling through the swarm of prying people.

9:30 a.m. The Metropolitan Police's headquarters is a hive of activity. David, the computer technician remains silent whilst Beth relates the story. By his puzzled and thoughtful look, you can guess the news comes as a complete surprise to him.

The agenda for today's briefing consists of a unique item: under no circumstances should anyone leak any information about the current inquiries. The inspector ends the meeting with a muted applause and his favourite phrase: "Do I make myself clear?". The instructions are as clear as day.

The special operation command has been working hard since the first body was found 21 days ago. Nine deaths, all poisoned. Nine stations, each from a different line. But, things are seldom as they seem. David had requested an urgent meeting on Tuesday to announce an unexpected connection between the deaths. Unfortunately, the meeting, postponed until Wednesday, was broken up after the room's door burst open and constable Beth announced the 9th death. David was talking ten to the dozen, trying to shed light on the recent deaths. He looked at Beth and came out with a name. "Heathrow Terminal 5 station". Beth nodded at him in agreement. The news left the inspector speechless. A deathly silence fell on the room.

A few minutes later, David managed to resume the speech, giving detailed account of his findings. The connection between the string of deaths was purely and simply numerical. Looking at the calendar on the wall, David reeled off the first few numbers that were crossed out: 1, 2, 3, 5, 7, 11. It was a well-known sequence, and as yet no officer had discovered the link. Prime numbers. The team looked on in awe as David rendered the second discovery: the stations had not been chosen at random. They also followed a clear pattern: the last station of a line, the line chosen in alphabetical order. A two-slide Powerpoint presentation showed a couple of Wikipedia articles supporting the explanation.

To be continued...