Objects genuinely moving on their own - how to investigate vs how to not go insane

My sister's been experiencing poltergeist activity in her flat in Manchester for about three weeks now. Cutlery moving off the counter, a drinking glass that was on the table ending up in the sink (no one put it there), doors opening, that sort of thing. She's understandably freaked out.

I want to help her investigate this properly, not just go 'ghosts!' or 'you're mad!' - but I'm worried about two things: (1) looking like absolute muppets if this turns out to be explainable, and (2) if it IS something weird, accidentally making it worse by doing something wrong.

Where do you even start with poltergeist activity? I've seen some guides online but half of them involve sage and crystals which my rational sister will absolutely reject. I want empirical approaches - filming, motion sensors, environmental monitoring. What's the actual proper first step?

Good instinct on wanting proper methodology. Poltergeist cases break down roughly into: (1) explainable household stuff - pets, vibrations from heavy traffic or construction, loose fixtures, (2) psychological factors - stress, adolescents in the home can actually cause weird activity through unconscious movement or prankery, and (3) genuinely anomalous. Start with (1) and (2) first. Get a surveyor in, check for subsidence and vibration sources. Ask your sister if she's under unusual stress - honestly, stress can cause people to move things without realizing. Not consciousness faking it, just neurotic habit.

For actual monitoring without the woo: basic CCTV cameras (you can get decent ones for under £100), a notebook documenting every incident with time/date/what happened, photos of the areas involved. Temperature and humidity monitoring can sometimes correlate with activity. Motion sensors are useful too. The goal is ruling out natural causes rather than proving anything paranormal. If you can't find a natural cause after two weeks of documentation, then you start considering other possibilities.

Honestly? Most poltergeist cases that get properly investigated turn out to be explainable. Floorboards settling, pipes hammering, someone sleep-walking, a family member playing pranks (even unconsciously), mice in the walls making noise. I'm not saying that's definitely what's happening here, but statistically that's where the smart money goes. Your sister should also consider if her mental health is okay - genuine distress can manifest as weird perceptions of normal events.

The Manchester flat detail matters - older properties or newer builds? Older ones have more settling and movement. Also, which floor? Ground floor with water pipes underneath? That can cause all sorts of unexplained noises and vibrations that people interpret as paranormal. Get the basics ruled out first, mate. Then if it's still happening, come back and ask about more esoteric approaches.