Walker heads a team of four carefully trained New Zealand police officers, and his operation called Nvaders heads off every two months to Thailand and Bangkok where they hit the ground running.
Southeast Asia, known for glorious tourist package-deal holidays, is also infamous as a vice hot spot.
When Walker and his team walk the crowded Bangkok streets it seems every street is a red-light zone with young - very young - women flaunting their mostly tiny bodies to any male regardless of age or size. The only attraction is his wallet.
Child pornography and child prostitution is a specialty here.
Every warped paedophile want is a catered for. It's hideous.
Walker and one of his team get close to finding where the 2 to 4-year-olds are kept. We see them heading off down a dark, murky alley led by a local man. The tension grew but a last-minute inside tip meant the heavily padlocked shipping containers in the lane had been hastily emptied.
The same scenario with young girls aged between 9 and 14 who were moved after a tip-off that a police raid was about to spring.
The worst thing is these tip-offs are usually an inside job from someone local working with police.
Viewers who were hoping this documentary would be a slice of entertainment would have switched over before the first ad break.
This documentary clearly emphasised the compassion and dedication needed to pull these women and children free from the filthy jaws of the Asian sex trade.
Chaps like Walker are among those rare beings: committed, caring and compassionate.
