If your game is top down and the enemy object has "pathfinding" behavior
1- compare player distance to enemy distance ... Add event - System - compare two values - first value is dhe minimal distance the player can move close to the enemy without being detected ( you decide that) is smaller "<" than the second value , which is (player.x,player.y,enemy.x,enemy.y)
2- on the same event ad another condition - if player is not sneaking ... i would use a local variable for the player , sneakint=1 or sneaking=0
If player is not sneaking , so sneaking=0 than this second condition is true .
3- add action - enemy - find path to (player.x,player.y)
4 - new event - enemy - if path found - fallow path ...
In case your game is a sidescroller with gravity , i think you will find a way for the enemy to go to the player