There's mystery surrounding the 50-year-old time capsule buried at a former theater in Clear Lake, and Jim Johnson can't wait to dig it up. Artifacts likely include an American flag taken by astronaut Charles Conrad on a space flight, astronaut Charles Bassett's speech for the dedication of the library, clippings about the theater's opening, an enrollment projection for Clear Creek school district and a model of a space rocket. Former NASA official Milt Heflin, who was most recently an associate director at the Johnson Space Center, will be a special guest at the event, which will take place at 16602 El Camino Real, Houston, which was most recently the site of a restaurant that went out of business.