It is 4am on a cool winter morning and a man in shorts is standing outside the front door of an apartment desperate for help.
He isn't homeless or a beggar - just a poor fellow who forgot to grab his keys when he went to throw out the rubbish.
That night the hero is young locksmith Chris Mak Chi-wai, summoned by the management office at the apartment block.
There are plenty of locksmiths in this city, but Mr Mak, 32, is among the few who offer a 24-hour service. He runs Fai Tat Locksmith with his uncle Wong Fu-kan from a stall in Wan Chai's Gresson Street wet market, and he cuts keys, sells all kinds of luggage and door locks and installs and opens locks.
But it is the 24-hour emergency service that is his best earner, representing about half of the venture's income. Sometimes he gets several calls a day and occasionally more than 10.
'It is not a kind of business that would make you a millionaire but it is a good job in which to earn a reasonable living,' said Mr Mak in his about 100 sq ft wet market stall next to a florist owned by his mother.