What's supposed to be a mere practical joke to ""embarrass the Government""--knocking guardsmen off their horses with tranquilizer darts--becomes an altogether different matter when the second victim is permanently silenced. The well-paid marksman, Vince Chapman, happens to be a disgruntled Special Branch Chief Inspector. He's being coerced by some masked individuals who hope to deter dÃ‰tente by the cancellation of Brezhnev's impending state visit. Chapman's old colleague Len Wilson comes out of retirement to help crack the case. . . several more slayings follow. . . and you should find this a reasonably well-executed if nebulous bit of target practice.