Shadow Sneak is an ability for Night Cap in Plants vs. Zombies: Battle for Neighborville. It allows Night Cap to completely cloak herself from zombies for 3 seconds and allows her to move faster. During the duration, occasional smoke clouds will appear where Night Cap is. You can stack up to two uses of Shadow Sneak.
Disappear and move swiftly.
Shadow Sneak is useful for getting into a combat. Use it to get close to an enemy undetected, then use Spore Strike or Fung Fu to get a quick vanquish.
Shadow Sneak is also good for exiting a battle. If at low health, you can use Shadow Sneak to retreat then hide nearby, safely regenerating health. Watch out, however, as players can see the smoke clouds you leave behind.
The main giveaway for a Night Cap using Shadow Sneak is the smoke clouds. If you see them, shoot them. You'll be able to hurt the Night Cap, as they aren't invulnerable while they're invisible. The Engineer is best, as his splash damage will almost always hit the Night Cap, while other zombies may miss as the Night Cap gets increased speed while using Shadow Sneak.