With the home side hot on attack, Peta Hiku attempted a pass which didn't need to be thrown. It was intercepted by Tautau Moga, who sprinted 90m to open the scoring in the sixth minute.
The Kiwis drew level on the scoreboard through Foran, who showed great strength to force the ball near the posts.
Samoa deservedly regained the lead in the 18th minute, Daniel Vidot beating Manu Vatuvei to a precise Kyle Stanley grubber.
Vatuvei were harshly denied a try in the 33rd minute, disallowed for an 'obstruction' several phases back in the extended movement.
The Kiwis were expected to lift in the second half but Samoa extended their lead in the 44th minute through Leilua, the Knights centre showing astonishing strength to bulldoze through three Kiwi defenders.
The home side just couldn't get going but Nightingale's 64th minute try gave them a glimmer of hope.
They still trailed though - and it looked ominous for the Kiwis, before Kenny-Dowall's late, late score created by a Nightingale offload and some quick hands.
New Zealand: 14 (K. Foran, J. Nightingale, S. Kenny-Dowall tries, S. Johnson goal); Samoa: 12. HT: 6-8.