The report from the chemical analysis lab arrived, and it was precisely what Arthur was waiting for.
Creating a poison, while it sounds easy, is only simple if it's meant to merely harm someone. In that case, you just mix a bunch of random chemicals together. But to kill someone almost instantly? That's definitely not easy.
Looking at the results of the residue analysis, the lab team had followed Arthur's request to clearly label the danger level of each individual substance and investigate their rarity and difficulty to obtain.
And here, more than half of the preparations were not things that could be purchased normally. Only individuals with a license were allowed to handle them.
This further increased the suspicion on Scott, a chemical sorting plant worker who could access many dangerous preparations that a teenager like Martin couldn't get his hands on.
However, in Arthur's eyes—who was looking at the entire case from a panoramic view—this was nothing short of a crucial piece of evidence, leading him to the true identity of the real culprit.
The real culprit was someone who had provided Martin with this poison, helping him carry out the crime.
The real culprit must have had a network to genuinely make contact with Arthur and give the poison to him.
With just these two things, the scope of suspects narrowed down significantly. At the very least, it was no longer as hazy as before.
And Sarah, who had also been elevated by Arthur to see the panoramic view, was now filled with vigor.
This time, she even guessed correctly.
"A 13-year-old has very limited mobility, so we can probably check each potential target one by one, like the school."
Sarah asserted. For a teenager still in school, the school is the place where he can access the most people, because it's simply a microcosm of society. Even if Martin's point of access wasn't the school but another place, there's a good chance he got to that place from school.
Arthur nodded in agreement, adding a bit of his own opinion.
"In this case, we are assuming that a 13-year-old, a nascent killer like Martin, fundamentally doesn't have the ability to create such a clean case with so few clues on his first try. Therefore, he must have been guided by someone."
"At the same time, this case wasn't just about killing someone and then hiding clues at the scene. It also required a certain understanding of Martin's surroundings. Only then could a plan be created to stir up animosity between Scott and the priest, and then use that as a basis to make Scott a suspect."
"Even information about Martin himself, to be able to turn a boy into a murderer, must have been clearly understood. In other words, the real culprit at least needed to know Martin's basic background, selecting him as a suitable subject to be corrupted with a crime."
"This is a complete chain of information, especially Martin's background, and I don't think any place has a higher chance for someone to get a hold of Martin's background without arousing suspicion than the school."
Here, Arthur stopped, but his thoughts didn't.
To do the above, the person would have to be at least a teacher.
But that was a bit too presumptuous, so Arthur's plan was still to go and investigate first, then proceed.
Thus, Arthur and Sarah temporarily split their investigation into two directions.
Although there was a lead on the real person, the online investigation path could not be ignored. Even though they couldn't get a warrant for Martin's personal data right now, they could still investigate his public interactions and behavior on social media. If there was enough basis for criminal behavior there, they could apply for a warrant.
This would be Sarah's task.
Meanwhile, Arthur would, of course, be in charge of the on-site investigation at the school.
He would pose as a father visiting the school, with the reason being that he wanted to see if he should enroll his child there. Arthur did not display his police badge, even though it could make the investigation easier, because it could alert the real culprit who was in hiding.
Arthur couldn't let the culprit know that "the police have come all the way here."