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I have managed to get to the part where I have to get into the Theatre. However, there is a small problem; there is as far as I can tell, not a single place I can hide when going from the office to the theatre that the dog will not spot me. This includes being on the far side of the covered wagon (which the dog managed to spot me behind, even though the line of sight was through 4 walls, and dark).
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Try using this walkthrough -
Probably too late for you, but for anyone who comes later, neither the guard nor the dogs will hear you, just see you if you are generally in front of them. You can sort of hide from the guard, but not from the dogs.

For Secret of the Silver Earring you absolutely need a walkthrough but I've noticed they get this part wrong, so here it goes.

First part: run towards the guard and ready the key; when the view changes follow him walking until you reach the center of the screen then wait. Not so much hiding but waiting. Make sure there's an unobstructed line between your position and the small unlighted area between the two lampposts. Let the dog move to the right; when he approaches the top of the second lamppost, run towards the door, thru the unlighted area between the lampposts. When the view changes you might have to backtrack a little before reaching for the door. Remember to click at the door's base to enter. It's quite easy if you follow the correct path, and the timing is not very hard.

Second part: a bit trickier. You must hide from the guard first, then run away from the dog's gaze. Ready the key before leaving. When you leave the building, run to the bottom right of the screen as fast as you can and keep running until you stand close to the covered wagon, on the right. Don't worry about hiding from the dog, hide from the guard as best as you can. Let the guard approach. When the dog is walking in the unlighted area between lampposts, quickly run around the wagon, close to it until you circle it, then run in straight lines towards the theather in center left. You can only run when there are no obstructions between you and your destination. The view will change briefly, don't be disoriented and keep running towards the door. When the door shows run towards it and double click with the key at its base to open it.

Congratulations! Now enjoy the most infuriating scene in the game.