Lina did something she had never done before. She took the lift down to the third floor at 3:15 AM.

Unit #03-12. Three floors directly below her. The Lim family had lived there. Old Mrs Lim had passed away in 2019—peacefully, in her sleep, in the very bedroom that now showed occupancy at 3 AM. The flat had been empty ever since, caught in some legal tangle over ownership.

She almost pressed it. But then the light in the corridor flickered—once, twice—and the door of #03-12 creaked. Not opened. Just creaked. As if someone on the other side had leaned against it.

“Mrs Koh, I’m going to tell you something that isn’t public yet. The One View app uses a machine learning model trained on five years of sensor data from over 100,000 flats. Last month, the model started identifying a new category of event. We call it a ‘persistent non-resident signal.’ It shows up in blocks that have experienced… let’s say, sudden vacancies. The model doesn’t know what it is. Neither do we. But it’s now appearing in over 2,000 flats islandwide.”

It started with the HDB One View app. The government had rolled it out quietly—a single portal for everything. Want to check your outstanding service and conservancy charges? One View. Report a noisy neighbour? One View. Apply for a new toilet bowl under the Home Improvement Programme? One View. It was the bureaucratic equivalent of instant noodles: convenient, soulless, and strangely addictive.

Lina, a 48-year-old accounts manager with a weakness for efficiency, downloaded it on a Tuesday. She linked her Singpass, authorised the biometric scan, and watched as her flat materialised on the screen as a glowing 3D model. There it was: #09-12. Three bedrooms, two baths, a balcony that faced the expressway. The app displayed real-time data—water pressure, electrical load, even the carbon dioxide levels in her living room.