The Sandmen (2000)

Original title: Les marchands de sable

Alain runs Le Detour, a small cafe in Paris where Antoine works. Antoine is reunited with his sister Marie when she's released from prison; they are very close, perhaps abnormally so, but she's not aware that Antoine has fallen into cahoots with Stephane, who works as a waiter at another cafe. Damien, a local businessman, is pressuring Alain to expand Le Detour, and cut his nephew Xavier in for a percentage as a manager. While Alain waffles on Damien's proposal, Xavier offers Antoine a chance to make some money under the table by delivering some drugs to a cadre of dealers. Antoine makes the drop and picks up the payment, but runs off with the money rather than bringing it back to Xavier, which proves to have tragic consequences for Antoine and his friends.