Midnight Oil

The Midnight Oil was a chemical weapon in gas form created by Howard Stark, which he classified as one of his most dangerous.

Theft and Retrieval
Former Leviathan operative Leet Brannis stole the Midnight Oil from Howard Stark's vault under his mansion, under orders of Leviathan to retrieve the item.

Brannis, wanting to make profit for himself, stored the gas along with the rest of Stark's inventions on a boat named The Heartbreak, guarded by Jerome Zandow, who could not prevent Peggy Carter from finding it, and the item was later claimed by the Strategic Scientific Reserve, who took the inventions into their custody for study.

Pictures
Peggy Carter, using the Camera Pen, took a picture of the crate that contained the Midnight Oil, labelled as Item 17.

Dottie Underwood found the photograph when she infiltrated Carter's apartment in the Griffith Hotel.

Leviathan Weapon
Doctor Ivchenko, posing as a former prisoner of Leviathan, hypnotized Chief Roger Dooley to retrieve the gas, and ordered him to wear the Explosive Vest to provide a distraction while he escaped from the New York Bell Company Office.

Dottie Underwood picked-up Ivchenko, who informed her that they needed to test the effectiveness of the weapon before using it.

Underwood released the gas from one of its canisters inside a movie theater, locking the patrons inside, and they started to brutally attack and kill each other.

Sprayed
While investigating the movie theater massacre, Daniel Sousa accidentally inhaled the gas when he found the canister. He began coughing and choking; drawing the attention of Jack Thompson. Sousa attacked Thompson and started to strangle him. Peggy Carter went to assist Thompson; Sousa slapped her away. Eventually, Sousa fell unconscious.

When he awakened, strapped to a bed, he did not have a clear memory of what he had done.