  In {\cal N} = 2 superconformal three-dimensional field theory the R-symmetry
is determined by locally maximizing the free energy F on the three-sphere.
Using F-maximization, we study the {\cal N} = 2 supersymmetric U(N_c) gauge
theory coupled to N_f pairs of fundamental and anti-fundamental superfields in
the Veneziano large N_c limit, where x = N_f / N_c is kept fixed. This theory
has a superconformal window 1 \leq x \leq \infty, while for x < 1 supersymmetry
is broken. As we reduce x we find "a crack in the superconformal window" - a
critical value x_c \approx 1.45 where the monopole operators reach the
unitarity bound. To continue the theory to x < x_c we assume that the monopoles
become free fields, leading to an accidental global symmetry. Using the Aharony
dual description of the theory for x < x_c allows us to determine the R-charges
and F for 1 \leq x < x_c. Adding a Chern-Simons term removes the transition at
x_c. In these more general theories we study the scaling dimensions of meson
operators as functions of x and \kappa = |k| / N_c. We find that there is an
interesting transition in behavior at \kappa = 1.
