Cambridge police yesterday assigned two detectives to solve the theft of more than $250 from Liberal Union film proceeds.

Milton S. Gwirtzman '54, president of the Liberal Union, requested police investigation after the group noticed losses of $250 following two films, and $30 after Tuesday night's performance. Originally $180 was stolen Tuesday, but $150 of it mysteriously turned up in the New Lecture Hall yesterday morning.

Carl A. Wagner '53, chairman of the H.L.U.'s film series, discovered the theft Tuesday following the showing of Alfred Hitchcock's mystery, "The 39 Steps." He found the total number of ticket stubs--more than 1,000 selling at 60 cents apiece--were in excess of the net income of $534. Wagner estimates income should have been approximately $700.

Ticket-sellers used two tables in the foyer of the New Lecture Hall, Wagner stated. Other than the ticket stubs, which are dropped into a box at the Hall entrance, there is no check on the night's proceeds.

Tuesday night Wagner sold at one table and Leroy A. Huntington '53 was in charge of the other. Other members of the organization were at the tables at various times during the evening.

On discovering the loss, Wagner said members searched the hall for two and a half hours. They examined the ticket box and looked under the tables--in vain. The money was gone.

At 12:30 a.m. yesterday morning, they gave up the search. The red ticket box was placed in a closet by the janitor, and the closet locked.

At 9:45 a.m. yesterday, Wagner said that Huntington, one of the ticket-sellers, suggested searching the ticket box again.

"We went over together," Wagner said, "and asked the janitor to open the closet. We took out the box, and jammed between two change tills was a roll of $150 worth of $10 and $5 bills.

"Something is fishy, because we examined the box before locking it up," Wagner said.

Gwirtzman said he was not sure exactly how much money had been stolen at the other two performances. "The system had been so slipshod we couldn't be sure how much the total was," he said.

But at the end of both nights, it was noticed that ticket receipt totals were more than net income. Suspicious, H.L.U. members carefully cross-checked receipts and ticket stubs at the showing of "Stairway to Heaven." There was no loss.

At least one of Tuesday's ticket-sellers, however, did not work at the "Stairway" performance.

Police said the case is a "must solve."