  We show how the area theorem is applicable to the analytical description of
the nonlinear interaction of surface plasmon modes with resonant two-level
atoms. A closed analytical solution is obtained, which shows that surface
plasmons can form long-propagating $2\pi$ pulses when interacting with an
optically dense two-level atomic ensemble. The possible applications of the
surface pulse area theorem and the conditions for the detection of $2\pi$
surface plasmon pulses are discussed.
