There's nothing rotten about Quad City Music Guild's current production of Dirty Rotten Scoundrels; Thursday's preview performance was delightfully wicked from beginning to end. There is, however, plenty that's dirty in this musical stage adaptation of the 1988 film, which starred Michael Caine and Steve Martin. The raunchy humor is sharp and smart, including the plethora of usually groan-worthy double entendres, and it's all delivered remarkably well by director Greg Bouljon's cast.