It's March in Sable Michigan, and Ruby Crane has nothing to look forward to but a month of dirty snow, mud, and cabin fever -- and if that's not bad enough, her estranged older sister Phyllis -- a successful and beautiful engineer -- has arrived in town for an unannounced visit, and she's asking for Ruby's help.

Phyllis's last project -- designing a spillway for a mineral mining company -- ended in disaster when some kids homing around after hours climbed into the spillway and it collapsed beneath them, causing the death of one teenager. Their families are suing Phyllis, claiming that her flawed design was responsible for the death; and Phyllis needs to prove that the blueprints the mining company have in their possession are forgeries. Only Ruby's expert opinion as a graphologist can prove Phyllis's innocence.