an intriguing feature of the explicit charged (reissner-nordstrom) or spinning (kerr) black hole spacetimes is the existence of a regular cauchy horizon, beyond which the einstein equation loses its predictive power. the strong cosmic censorship conjecture of penrose is a bold claim that, nevertheless, such a pathological behavior is nongeneric. in this lecture, i will give a short introduction to general relativity and the strong cosmic censorship conjecture. then i will describe my recent joint work with j. luk, where we rigorously establish a version of this conjecture for the einstein-maxwell-(real)-scalar-field system in spherical symmetry, which has long been studied by physicists and mathematicians as a useful model for this problem.