Everyone kind of agrees, Daniel Fenton was (or at least *had been*) in a cult. He seemed. . . normal enough, on the surface. Granted, everyone in Gotham was kind of weird, but he didn't stand out in many ways. Just passing him on the street, you'd think he's a normal twenty-something year old with a slightly odd fashion sense, but Danny's colleagues knew better. At his orientation, he was given a work phone. A perfectly normal, average, phone. To be used for work. And everyone there watched as Danny laughed and said (declared, really, in that awkward tone of his) that he had never used one before.
The older guys at the shop claimed he had an "old soul", which Danny laughed with them about, but even they started giving Danny odd looks when he didn't know common things about the world, or history, or advancements that everyone (even those older than Danny) had been taught in school. They tried not to mention it. Danny was smart and kind and funny and did more than his fair share, but the more he opened up to everyone, the more odd things became apparent.
His past has strange holes in it. He'd clam up when he had to mention specific locations, or names of places (besides some place called "The Nasty Burger", which he equated to the Batburger), and he always looked distinctly forlorn when talking about his friends and sister. He never spoke of his parents, and he always looked scared when someone asked about them in passing. Sometimes he would talk about someone named Vlad with a bit more cheer, even if Danny said they were "arch-nemeses", and he would always light up whenever anyone asked about his kids, even if he never mentioned another parent. (He did say Vlad had something to do with both of them, but never really elaborated. Mostly because he was distracted by some story about the man.)
His manners and habits were the strangest part of him, though. He'd often curse in a strange language none of them (or Google) knew or could identify, and when he did curse in English, he often referenced (or blamed, quite frankly) things on "Observants" or "Ancients". He'd hum to himself while he worked, one note, one tone, that seemed to go on for way too long. The rare times he'd eat lunch with others, his food was always moderately glowing, or it just looked. . . odd. (He always claimed his kids added something to it.) Sometimes he'd look confused about normal physical interactions, and once he tried to greet someone by crossing one arm over his chest and bowing.
Then there was a "bring your kid to work" day. It was mostly just a bonding activity for the team, but Danny looked quite excited by the prospect. He boasted about his kids the whole week leading up to the day. When he came to the party, he had a young girl hanging from his arm with a nearly devilish grin. She was nearly a carbon copy, and she introduced herself as "Danielle". Just when Mark (the man that sat next to Danny and dealt with most of his strangeness) was about to laugh about how Danny named her after himself, a rather burly man walked in and got to Danny's side. Danny beamed and introduced him as Dan, his son, despite the fact that Dan looked to be in his mid-thirties.
Yeah, everyone decided that day. Definitely a cult thing.