I've seen depictions of the sun's orbit about the center of the galaxy and it resembles the trace you'd get from a point on a merry-go-round horse as it gallops around its circle. It seems likely that as we pass through the plane of the disc that our chances of encountering substantial concentrations of dust and gas would be pretty high. It also seems that even though an optically dense region like the Horse Head Nebula is basically empty space, there might be significant effects to a planetary system passing through such a zone.
Would anyone care to remark on the possible consequences of such a plunge? Could we detect any effects later, say in ocean sediments or the lunar reggolith? Maybe in meteorites? Is it possible that the fractional increase in density of the interstellar medium might dump some comets from the Oort cloud? Periodic extinctions solved; read all about it?