A study with experimental and numerical components is conducted to establish the effect of a two-dimensional surface cavity on the structure and growth rate of a turbulent spot. The spot is artificially created in a two-dimensional laminar boundary layer developing under zero streamwise pressure gradient. Interactions of the turbu lent spot and its wake with the Kelvin-Helmholtz rollers of the cavity shear layer are shown to result in significant increases in its lateral and streamwise growth rates. The underlying physics of these developments are identified.