The best thing about an advisory panel’s plan to overhaul Maine’s prison system is that it will serve as an example of how not to do it next time.

We say next time because there must be one. This $160 million turkey just won’t fly. It is too expensive with too little benefit to be considered a prudent investment. It is too narrowly focused geographically, too neglectful of Maine’s northern two-thirds, to be politically palatable.

This entire exercise started, remember, with the discovery early this year that Maine’s daily per-inmate cost of $72 is among the highest in the land. The national average is $55. The solution seemed obvious: pare down the six aging, inefficient adult facilities; spend a lot on construction now and reduce operating costs for years to come.

Half of the panel’s plan for adult corrections makes sense. Close the dilapidated Maine State Prison in Thomaston and spend $64 million adding 432 beds at the Supermax in nearby Warren. There’s no displacement of staff — they’d practically be working across the street — and the per-inmate cost drops to $60.

It’s the other half that doesn’t add up. Add 566 beds to the Maine Correctional Center in Windham for nearly $45 million and the per-inmate cost plummets by nearly three whole dollars, to $69.43.

Meanwhile, as the state is adding more than 200 jobs at Windham, where there is virtually no unemployment, it is closing Down East Corrections Facility in Bucks Harbor, costing Washington County 72 jobs. Never mind that Down East, despite a wholly inadequate building that wasn’t built to be a prison, has long been one of the most cost-effective lockups in the system, with per-inmate costs ranging between $60 and $65. Never mind that it has the lowest staff turnover rate in the system. Never mind that Washington County has an unemployment rate stuck in double digits.

This probably would not have happened had the 15-member governor-appointed committee not done most of its work before it realized it had no representation from north of Augusta. This probably is why the absurd argument that a substantial prison, perhaps a minimum-security lockup, Down East would be an unconscionable hardship for Southern Maine inmate families on visiting day got taken seriously. A Washington County member was added late in the game, but it was too late. The decision had been made, the deal was done.

Oh, the panel did toss a bone Northern Maine’s way at the final meeting — a promise that Washington County might get something called a resource center for counseling, education programs and probation checks. More accounts for professional counseling types, maybe a few beds, maybe a few jobs for regular folks. There’s no real numbers or money attached, so nothing’s definite.

Here’s the score: Southern Maine, $108 million in construction work and hundreds of new jobs; Northern Maine, zip. A fortune spent building two new prisons within 60 miles of each other and only a minimal improvement in operating costs. Families in Biddeford can walk to see Uncle Roy in the Big House, while families in Washington, Aroostook and Piscataquis get to turn visiting day into a mini-vacation. Such a proposal probably won’t get past the Legislature and it certainly won’t get past the voters at bond-issue time.

Gov. King hinted at as much the other day when, while not commenting on the specifics of the plan, he observed that such a huge undertaking would have to be done slowly, in phases, and that big bond issues for corrections have not fared well at the polls.

Combine that with the governor’s recent strong support for fixing the mess that is Maine’s juvenile corrections system and the near-term course is clear: spend money now — the panel recommended $25 million — to make the Youth Center buildings habitable and its programs truly rehabilitative; then send the adult prison side back to the drawing board and get it right.

Next time, get the entire state involved from the start. Next time, come up with a plan that delivers a real return on investment. Next time, give a thought to Northern Maine families. They have black sheep and they miss them, too.