Level walkthrough: Head forward after you've started the mission and you'll find a gate with three skulls. Examine this entire area with your PKE meter and it shouldn't take too long for you to find the first artifact - Whistling Bust of Mausch. Move back a little and locate a hole in the brick wall to enter cemetery grounds.
You may now start exploring your surroundings freely, especially since you won't encounter any monsters here. Ignore graves coming out of the ground, because you can destroy them easily with your primary weapon. Eventually you should be able to get to the section filled with more graves.
Continue moving forward. You shouldn't have any problems finding the correct path, because you'll be surrounded by obstacles from all sides. Focus on reaching a small chapel. Approach the entrance and notice skulls flying out of the building. They won't attack you and you won't have to take any scans, because the skulls are already in your database.
Don't enter the mausoleum right away. Instead head over to your left and inspect the area around a smaller crypt. Naturally, you must use your PKE meter here to uncover the location of the second artifact - Ghostbuster's Mug & Balloon. Go back to the mausoleum, enter it and use the stairs.
Get rid of the black slime and then use your Proton Gun to unlock a nearby passageway. You'll be dealing with similiar obstacles in the area, but thankfully destroying them is going to be easy. Focus on finding the exit from this tunnel complex. This will allow you to reach an isolated area of the cemetery.
I assume that you may have some problems figuring out the next step. Stand in front of a GATE CONTROL sign. You'll have to use your capture beam on the metal object. Once you've captured it press the key responsible for the slam attack. This will allow the object to touch the ground.
Notice that Ray has joined you and you'll have to follow him into a new crypt. Once again you'll be allowed to move fast, because you won't encounter any ghosts here. Choose a very narrow passageway located next to the fence. Watch out, because the next area of the cemetery is being guarded by hostile creatures.
Obviously you should begin by taking scans of two unknown creatures - Grave Fiends and Cemetery Crawlers. You'll also be dealing with Cultists, but you've already had a chance to add them to your database. During the battles focus on keeping Ray alive, because if he gets knocked down you can also die easily and it'll be game over for you both.
I would recommend that you keep using the Proton Gun, because this weapon will be effective against all kinds of threats, so you won't have to switch guns too often. Don't forget that you must trap Cultists if you want to get rid of them for good. Also - neutralize nearby portals as soon as possible, so it'll stop more monsters from crossing dimensions.
Destroy large obstacles located between two street lamps. Doing this will allow you to get to the next area of the cemetery. Set fire to a hedge and explore the area near the crypt. The second artifact (Stone Angel Head) is hidden nearby.
You may proceed to the next section. Watch out, because you're going to be attacked by new ghosts upon your arrival in a slightly larger area. Notice that it usually takes a single Boson Dart to kill Grave Fiends, so you can eliminate them quickly. Pay more attention to powerful creatures, including an entirely new Cultist Summoner.
It would be a good idea to use the Meson Collider against the summoners, however the Proton Gun can also inflict serious injuries as long as it's properly used. Once you've won follow your colleagues and you'll soon end up standing in front of the entrance to a new crypt.
Thankfully you won't travel through an entire underground complex, because you'll soon find the exit from the mausoleum. Head forward and eventually you'll come across a large gate. Watch a new cut-scene, turn right and get ready to defeat a small group of less powerful creatures.