  We present a non-perturbative analysis of the power-spectrum of energy level
fluctuations in fully chaotic quantum structures. Focussing on systems with
broken time-reversal symmetry, we employ a finite-$N$ random matrix theory to
derive an exact multidimensional integral representation of the power-spectrum.
The $N\rightarrow \infty$ limit of the exact solution furnishes the main result
of this study -- a universal, parameter-free prediction for the power-spectrum
expressed in terms of a fifth Painlev\'e transcendent. Extensive numerics lends
further support to our theory which, as discussed at length, invalidates a
traditional assumption that the power-spectrum is merely determined by the
spectral form factor of a quantum system.
