“Stink!” opens with a foul smell and a pair of kids pajamas. And a single father trying to find out what that smell could possibly be. But instead of getting a straight answer, director Jon Whelan stumbles on an even bigger issue in America, which is that some products on our store shelves are not safe — by design. Entertaining, enlightening, and at times almost absurd, “Stink!” takes you on a madcap journey from the retailer to the laboratory, through corporate boardrooms, down back alleys, and into the halls of Congress. Follow Whelan as he clashes with political and corporate operatives all trying to protect the darkest secrets of the chemical industry. You won’t like what you smell.