The couple's every hope is pinned on Detective Superintendent Harry Shepherd and 70 officers who are working round the clock to reunite them with the infant taken from her father by a bogus nurse just four hours after she was born.
Six days after the abduction, detectives have yet to find, or make contact with, the baby or the woman who spirited her away, and faint grumblings about their softly-softly strategy are audible.
Hindsight is, of course, a perfect science and the police know there will be little mercy should the tragic drama not reach a happy conclusion. The public and press reaction to a botched job might be ferocious. But, with his close contact with the Humphries family, Det Supt Shepherd must already bear the heavy weight of personal responsibility.
The next 24 hours may bring a watershed. Senior officers must decide whether to release security video pictures of a rear view of the suspect and a vital witness if the abductor fails to respond to Det Supt Shepherd's recent moving appeal to the kidnapper, devised by Paul Britton, a leading psychological profiler.
Daily press conferences are increasingly tense. Predictably, there have been complaints from journalists that they are not receiving enough information to keep the story going.
The whole delicate enterprise is plagued by risk. Until now police have acted on the theory that Abbie's abductor is a woman who has perhaps lost a child or is unable to have one of her own. The emphasis has been on sympathy with the promise of understanding and help if she gives herself up. This kind of abductor, reason insists, does not steal a baby to harm but to care for it. This kind of abductor, the theory goes, can be emotionally reached and her conscience appealed to.
Release of the video pictures was delayed because psychologists have warned they might panic the abductor and put Abbie at risk. But to delay their publication is to risk a later charge that the police procrastinated on the advice of shrinks and failed to use the one weapon that might have speedily reunited the family.
'It is a case of damned if you do and damned if you don't,' said Dr Ian McKenzie, a former policeman and lecturer in police studies at Portsmouth University.
'But as a psychologist and police officer, I'm delighted at the extent to which police officers have consulted with psychologists. The old style police officer thought that anything with an 'ology' at the end had nothing to offer the practical policeman.'
Dr McKenzie believes the strategy adopted so far has been correct. Rash action might have been tempting in the face of such strong public feeling. He compares the abduction to seiges that can end in catastrophe when patience runs out and precipitous action is taken.
The waiting must be excrutiating for the Humphries. According to another psychologist, who does not want to be named because of the delicacy of the situation, it can be almost as painful for police officers, when they are forced to become part social worker, part law inforcer.
'Policemen generally want to get things over and done with quickly. They like to act, get a result and bring distress to an end quickly. Then they get an offence which defies all that. It requires a different kind of psychological rhythm, one that is not valued by some people. But I think they have acted impeccably in this case.'
The psychologist claims that behind the hype and 'bullshit', psychological profiling is really a mixture of common sense, reason and empirical experience. In cases like Abbie's it can help predict what kind of person, with what attributes, would behave in a certain way.
It may be more successful in identifying the abductor than a demanded photofit or vague video picture, he claims. While the public 'are notoriously bad' at recognising distorted images, they may be more skillful in spotting a woman who has recently moved to the area, may not have a partner and who has just began to care for a baby. The release of a picture might also 'paralyse' the inquiry with an avalanche of well- meaning but essentially useless information.
But he warns that no amount of theory can allow for the impulsive or unpredictable act or the offender who does not remotely resemble the expected profile.Reuse content