|Plot details follow, read at your own risk.|
Central Police Station
- "Be careful Phelps. This is his game you're playing now."
- ―Ray Pinker.
The mission starts with Phelps meeting in tech services with Captain Donnelly, Malcolm Carruthers and Ray Pinker. After going through a few 'gifts' from the Black Dahlia (B.D.) Killer, Phelps realizes that the B.D. Killer is actually taunting them. He figures out that the poem they have been given translates to landmarks around Los Angeles.
|Black Dahlia letter|
|"Note from Black Dahlia killer composed of newsprint, rinsed in gasoline"|
|"First Extract from 'Prometheus Unbound', by P. Shelley"|
- "Him. It's really him. The fuck who killed the Dahlia. Can you believe this? He's leading us..."
- ―Rusty Galloway
|Elizabeth Short's Social Security Card|
|"Elizabeth Short's Social Security Card"|
|"Second Extract from 'Prometheus Unbound', by P. Shelley"|
Hall of Records
Cole deciphers the second stanza to be describing the Hall of Records, and the chandelier hanging from the ceiling. Cole makes his way to the top of the chandelier by carefully balancing on the chain and walking across. In the center he discovers Deidre Moller's missing watch, and the third excerpt from the poem. Suddenly, the chains break causing Phelps to panic, he is forced to swing the chandelier in order to get it close enough to the balcony to jump to safety. (Done by swinging the left stick back and forth.)
|Deirdre Moller's Watch|
|"Deirdre Moller's missing gold watch"|
|"Third Extract from 'Prometheus Unbound', by P. Shelley"|
L.A. Public Library
Phelps decipers the third excerpt to be the L.A. Public Library. Phelps scales the outside of the building via a series of pipes, ladders, scaffolds and boards in order to reach the roof, where he finds Antonia Maldonado's missing religious pendant, and the fourth stanza of the poem. When Phelps returns to the ground, and reveals that he found Antonia's pendant, Rusty voices his disbelief at the fact the Dahlia has eluded capture for so long, he also urges Phelps to discover the next location.
|Antonia Maldonado's Medallion|
|"Antonia's medallion with 'Our Lady of Guadalupe'"|
|"Fourth Extract from 'Prometheus Unbound', by P. Shelley"|
Westlake Tar Pits
Phelps translates the stanza into referring to the Westlake Tar Pits where the prehistoric "monsters" have been preserved. Phelps makes his way to the island in the center of the pit, using the wooden walkways laid out under the tar. On the center Island, Phelps finds Theresa Taraldsen's shoe and the fifth stanza of the poem.
|Theresa Taraldsen's missing Shoe|
|"Lady's open-toed white shoe belonging to Theresa Taraldsen"|
|"Fifth Extract from 'Prometheus Unbound', by P. Shelley"|
L.A. County Art Museum
Phelps realises the "Spheres" mentioned in the last stanza is the armillary sphere in the center of the Maze at the L.A. County Art Museum. Galloway tells Phelps he has no intention of going in as he has heard the maze is tricky. Phelps travels to the center of the maze, where he finds Celine Henry's Ring as well as the sixth stanza of the poem. Seemingly a while later (as it is now dark), Phelps emerges from the maze, telling Galloway he found Celine Henry's ring and another stanza.
|Celine Henry's missing ring|
|"Missing ring belonging to Celine Henry"|
|"Sixth Extract from 'Prometheus Unbound', by P. Shelley"|
Solving the Maze
Enter the maze - use these instructions each time you have a choice:
- First right
Cole reads "'Thrones, altars, judgement-seats and prisons'... no, it couldn't be!"
Note: Backing your car, which appears in the Museum parking lot up the adjacent loading dock, will result in a "scene contaminated" case failure.
Phelps figures out that the previous stanza is leading them to the dilapidated Intolerance Set. Phelps and Galloway make their way up to the Throne. En route, Phelps gets trapped on a platform which he must keep balanced until Galloway can kick a piece of wood into jumping distance for Cole to get to safety. Phelps gets to the throne where he discovers Evelyn Summer's ring along with the Seventh and final stanza of the poem. The entire set suddenly begins to collapse and Phelps runs to safety via the scaffolding at the back of the set. He manages to get away safely. Back on the ground he tells Galloway that he has found the final piece of the poem.
|Evelyn Summer's typewriter ring|
|"Evelyn Summer's Ring made from typewriter "E" Key"|
|"Seventh Extract from 'Prometheus Unbound', by P. Shelley"|
Note: If you want a perfect rating (No damage to your car) or the gate won't bust open, have Rusty drive to solve this issue. Or, alternately, park outside the set and hop over the fence, which will also trigger the cutscene.
Christ Crown of Thorns
After Galloway mentions the whole thing seemed "religious", Phelps realises that the final location is a church, the decide to investigate the abandoned Christ Crown of Thorns church which is located several blocks away.
Phelps and Galloway enter the church armed, and find themselves face to face with the Black Dahlia Killer (equipped with a shotgun). It turns out to have been the temporary bartender, Garrett Mason. As a fire fight is about to break out, the detectives jump for cover, which gives Mason the chance to escape down a secret passage. They then pursue Mason into the Vicarage nearby.
Go left through the kitchen of the house and through another door. This leads the detectives directly into the killing den of the murderer, with a bloody bathtub, killing tools (including a bloody tire iron on the floor), and statue nearby (That is Prometheus, the inspiration to Garrett Mason). At the back of the room is a hole leading into the catacombs.
- "The city owes you both, but there'll be no mileage in ever bringing this up again."
- ―James Donnelly
Go down the ladder on the left side of the room into the church's catacombs. Phelps tells Galloway to call for backup and see where the tunnel leads. Chase Mason through the catacombs, being wary of cover and his hit and run tactics. You can turn on the Black and White option to see in the catacombs better.
After a lengthy chase through the tunnels, Phelps chases Mason up a ladder into a shed that leads into the graveyard. After a quick shootout, Phelps shoots Mason and kills him. The Black Dahlia Killer is no more, and a cut scene begins. During the cut scene, Captain James Donnelly lets Phelps and Galloway know that they must never speak of who the killer was, as he is the half-brother of one of the highest ranking elected government officials in America.
This ends the murder cases, as Cole is promoted to the Vice Desk. Note that it is possible to kill Mason while in the catacombs, Phelps will emerge back in the house, meeting Galloway and the captain.
- "The case of the Black Dahlia remains open, the truth lost to all but a handful of men."
- When Phelps and Galloway arrive at the Christ Church of Thorns, you can notice that there is a iron picket missing from the gate, the very same picket that was used to break in to Antonia Maldonado's apartment. This links Garrett Mason to the robbery.
- Elizabeth Short's true social security number is different from that in the game. In real life, it was 0-22-18-750
- It is likely that the Bloodied bathtub found in the Christ Church of Thorns is where Elizabeth Short (The Black Dahlia) was murdered and mutilated, her remains can be seen inside.
- A statue of Prometheus can be found near a bathroom sink in the house next to the church. If Phelps picks it up, Rusty says defying gods can be hazardous to your health.
- On the floor next to catacombs, there is a tire iron. If Phelps picks it up, he makes a claim, suggesting that arresting him would work for an airtight case, due to surplus of evidence. Galloway, however, disagrees, afraid that the probability of bringing Mason alive would be dangerously low.
- Garrett Mason can officially be first seen in the game working at The Bamba Club in "The Red Lipstick Murder", which is also Cole Phelps' first homicide case (making the killer himself, ironically the first person you talk to during the whole Dahlia string of murders). However, if you find the knife on the first sweep of Ray's Cafe in "A Marriage Made in Heaven", and return to Ray's, he will appear behind the bar instead of Dudley Lynch. However, he cannot be interacted with.
- As there are no interrogations in this case (one of the only missions in the game where this isn't required), the game awards experience points differently, beginning with 5 points for simply reading the letters at the start of the mission. Additional experience points are awarded for locating the landmarks as part of the ongoing Landmarks-related achievement (assuming the player hasn't already located the landmarks previously).
- The game telegraphs the solutions to the puzzles by placing question marks on the map at the various landmarks that need to be located; if the player has already hunted down a number of landmarks (or has found them incidentally during past cases or free roam) this actually makes finding the right locations more difficult as the question marks only appear for landmarks that have not previously been located in Free Roam, mission mode, etc.
- When Phelps and Galloway arrive at the Intolerance Set, Phelps' flashlight may not appear despite Phelps reaching into his jacket pocket and holding his hand up in the manner of holding an object. If this happens, simply opening and closing the notebook results in the flashlight appearing as normal.
- Completing this case unlocks the Homicide version of Free Roam, with a different set of Street Crimes to be solved.
- After Phelps' escape from the chandelier (and also after escaping the Intolerance Set), if the player has chosen a different outfit for this case (and thus his hat), he will still shake out the dark blue hat belonging to the Sword of Justice outfit, the default outfit for the Homicide cases. He will also wear the hat when traversing the Westlake Tar Pits.
- After traversing the Westlake Tar Pits, during the cutscene, Phelps can either be wearing his suit or the overalls he used to cross the tar pit.
- The fact that the case is still open is a reference to the fact that the Black Dahlia killer was never officially found in real life.
- In the first extract from Shelley: "To suffer woes which Hope thinks infinite..." is the final part of Prometheus Unbound in act 4.
- This is the second case featuring rain, the first being The White Shoe Slaying.