Tens of thousands of people vanish across the North West every year. In Greater Manchester alone, the figures suggest 65 will have disappeared today. Most will return, in time, but what happens to a family if their loved one doesn't?
Those left behind have no idea where their relative is, what he or she is doing, or why they severed all contact in the first place. They're thrown into limbo, longing for a single phone call or message and plagued by questions no-one can answer.
This week, I've tried to help four families in their search. Each has tried different methods to locate their loved one - from asking the authorities, to distributing posters, to putting photos online. Each has refused to give up, even when they've seemingly reached a cul-de-sac in their hunt.
What struck me most among the days of interviews and filming, was how these families scan an entire crowd within seconds to know if their loved one is there or not. It's a skill they've had to perfect. And I now find myself looking for 4 new faces at the petrol station, in the supermarket, or by the roadside as I wait in traffic.
The faces belong to Paul Fahy, Ciaron Nuttall, Steven Cook and Kevin Fasting. If you watch the videos below, then perhaps you'll look for their faces too - and, just maybe, spot one of them today.
If you think you've seen any of them you can call the Missing People helpline on 116 000. It's free and confidential. That number can also relay a message home from any missing person. Alternatively, you can click on www.missingpeople.org.uk.