It may start this way.

"Hey, kid, are you still hungry? Do you want another blanket?

"Do you want to know where your parents are? If your sister is OK?"

"Hey, kid. C'mere for a second."

Last week's reversal on family separation for undocumented border crossers is a welcome and humane development. But thousands of children remain in federal custody, caught between the desperate churn of flight and the grinding machinery of "zero tolerance." Thousands more continue to arrive unaccompanied and enter the same system.

I suspect that the great majority of men and women providing care to immigrant children are decent and honorable people.

But I also know that 1) a single serial child predator can do immeasurable damage to dozens of children, having accessed the right environment; and 2) current circumstances provide an unprecedented opportunity for them. Given the reality of child sexual abuse and exploitation, there are without a doubt predatory adults looking to infiltrate the now burgeoning system of child care that is taking place along the U.S.-Mexico border.

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These children could not be more helpless, and thus attractive to predators. They are, in most cases, penniless. Many speak little or no English. Some cannot write in their own languages. They usually have no means of personal electronic communication. They lack connections and political power. Whatever ailments they suffer, disabilities they face, or emotional turmoil they experience are a mystery to almost all who encounter them. We're assured by Secretary Kirstjen Nielsen of the Department of Homeland Security, that they are well cared-for.

Perhaps, but they are also well-watched.

If the wrong person gains access to the "right" child, that child will suffer. This is antithetical to the intent of the current (or any) administration, regardless of how it views immigration policy or undocumented persons. Yet this administration, more than any other in recent history, has invited the reality of child sexual abuse to flourish within its groaning, unprepared and overburdened system.

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Some of the burden, of course, cannot be helped. The administration cannot control how many children seek to cross unaccompanied, requiring custodial care. Likewise, no child protection system will ever be 100 percent safe, and previous administrations have also failed to protect their charges.

But it was the policy of this administration alone that added an additional burden and must now continue to carry it. Nielsen herself admitted that resources are limited when it comes to processing and handling these children, and this is understandable. Child protection is difficult and deeply expensive, and resources never match need. But such is the awesome responsibility of the task, which raises the question of why an already insufficient system sought to take on greater responsibility for it.

We can argue political philosophy all we want, but sexual predators, when it comes to the task at hand, are not political. They don't concern themselves with the nature of the criminal law or who is deserving of prosecution when it's transgressed. They're neither dismissive of nor weighed down by the Constitution, federal law, a sense of cultural change or a commitment to "justice," however defined. They don't judge parents who, for reasons heartbreakingly understandable or cynically fraudulent, take their children with them on their way to America. They simply wait on the other side for the opportunity to harm and exploit one of them when the opportunity presents itself. That opportunity is more in reach as a result of having treated all undocumented border-crossers for a time as criminals, subject to separation from their children. This is not a political statement. It is reality.

So go back to the imaginary conversation at the beginning of this piece. Imagine the predator, in a uniform, an apron, a T-shirt or a business suit, cajoling or just confronting a child he knows he has complete power over. A child lost and alone, isolated and defenseless. Imagine then whatever you dare.

Roger A. Canaff is a child protection and special victims advocate, legal expert, author and public speaker. @rogercanaff