Thorn Birds lovers, beware: you won't find the slightest resemblance between that romantic saga and this talky, strenuously high-minded tale of six Australian mental patients and their nurse. Set in a nearly-abandoned military hospital on a Pacific island just after World War II, McCullough's disappointing new novel focuses on 30-ish Sister Honour Langtry--who's sure that she makes a difference in the lives of the men under her care. She urges intelligent, graceful Capt. Neil Parkinson--from Melbourne's upper crust, like Honour herself--to talk out his anguish over a ""mistake"" which caused many deaths. She's soothingly sympathetic to hypochondriac Nugget Hones and blind Matt Sawyer. She's gentle with timid Ben Maynard, who cracked up when he realized he had fired on women and children. And she's even determined to help dazzling Luce Daggett--a cruel, vain former actor who both attracts and repels her. But what is she to do about her newest arrival? He's model soldier Michael Wilson, who doesn't seem to have anything wrong with him: sympathetic officers quietly shipped Michael to the hospital after he threatened the life of an officer who made a homosexual advance toward him. (Michael reacted violently because of the recent death of close friend Colin, a homosexual friend whom Michael pitied and protected without returning sexual love.) So Michael's quiet strength, his obsession with sheltering weaker souls, upsets the delicate balance among Honour's closely-knit, dependent group--especially when the men sense her attraction to Michael. And during one long night, while Michael and Honour sleep together, Neil breaks out a bottle of scotch (given to him by a blundering, pompous psychiatrist), and Luce--who has taunted Michael about homosexuality--is found dead, slashed and mutilated. The ward closes ranks; the death is reported as suicide; only when the hospital is finally evacuated does Honour learn the truth from Neil. And Honour and Michael will be separated forever: he needs, above all, to be needed (""I'm the sort of bloke who mightn't come home . . . because I found someone who needs me more than you do""); she knows ""her duty lay among those the world had forgotten,"" that her ""indecent obsession"" with duty is ""only another name for love."" McCullough never probes into the complexities of such crusading altruism--so the sentiments of Honour and Michael here have only a kind of tinny nobility. And, along with the wearying Aussie slang, there's a generally dated, faded feel to the entire novel--like an earnest 1950s stage-play or television drama. All in all, a far tweet from the Birds (or even from McCullough's modest, affecting Tim, 1974); but the very big name may well generate some fairly big sales.