As colonists from the entire solar system converge on the mother planet for the 2776 celebration, Duncan Makenzie--third of a "father-son" dynasty of clones--returns to Earth. Officially, Duncan represents Titan (Saturn's largest satellite, thriving on a brisk Makenzie-dominated hydrogen trade); but his more personally problematic mission is to clone a fourth Makenzie heir with the help of Terran genetic surgeons. Anything by Clarke is de facto an event, but this gentle, loosely plotted voyage of discovery is puzzlingly handicapped by trivial characterizations, Clarke's limited stylistic resources, and a general paucity of invention. Technological background and larger themes (has man been literally on the wrong wavelength to make contact with other intelligences?) obtrude on the narrative rather than reinforce it. Pleasant but oddly unformed.