'You like a smoke?' he asks, taking a long drag on his sweetly fragrant roll-up and leaning back against a pet-shop window.
It's just gone 10pm on a weeknight and a popular bar street in the centre of Shanghai is unusually quiet. We have barely met and this tall Nigerian has offered me a score almost by way of a 'hello'.
Marijuana fumes hang thick in the air, yet he seems unruffled by the police officer shuffling along the other side of the street. Welcome to Shang-high, where purveyors of 'rare herbs and proscribed chemicals' are 10 a penny.
For its size, Shanghai's drug problems are hardly overwhelming, especially when compared with major cities in developed countries. This is no New York, London or Paris. The vast majority of the 24 million people in the city earn far too little to blow money on blowing their brains - and are not so demoralised to want to do it regardless.
But times are changing, and the young, recently enriched are more easily parted with their cash. Not content with glugging down overpriced cocktails, some of them are starting to experiment with other substances. Wander past a trendy nightspot - the gaudy sort of warehouse-sized disco where they serve champagne with sparklers - late on a Saturday night and it's easy to spot the occasional wide-eyed stupor that it takes chemicals more complex than alcohol to induce.
In the past six months or so, things have been getting noticeably more blatant. The French Concession's Uygur dealers are no longer content to mutter about their Xinjiang wares from the shadows. They stride down the centre of the street brazenly calling, 'Hey, hashish-marijuana' at every Westerner or Bohemian-looking young Han they pass.
For something a little harder, it's customary to seek out the Nigerians. Shortly before the start of last year's World Expo, these backstreet pharmacists vanished almost overnight. They now seem to have multiplied several times over, having stocked up on goodies and staked out their claims for business districts. They appear well organised, interconnected and for the most part not overly pushy. The one thing they are not, though, is discreet: in a virtually ethnically homogenous city, black drug dealers are adhering to the sore-thumb school of camouflage.