In the 1930 comedy Up the River, two inmates break out of prison to help their former roommate avoid a life of crime. The film, which was a modest hit in its time, is largely remembered as the first and only movie that future Hollywood heavyweights and close friends Humphrey Bogart and Spencer Tracy appeared in together.

While making the film, Bogie and Spencer shared the experience of being New York stage actors freshly arrived in Hollywood. “They were both recruited into talkies,” explains James Curtis, author of Spencer Tracy: A Biography, exclusively to Closer.

Despite a professional respect that developed on set, Bogie’s drinking created a wall between them. “Bogie was a heavy drinker, but not an alcoholic, and Spencer had to watch that very carefully. He did not like being around heavy drinkers too much because it was too tempting for him,” explains Curtis, who adds that Spencer’s troubles with alcohol also impacted his friendship with Clark Gable, another hard drinker. “Spencer was constantly battling the impulse to drink. Sometimes he won and sometimes he lost. There were whole periods of time where he didn’t touch this stuff.”

By the dawn of the 1950s, both stars were at the top of their game. Spencer had become the first actor to win two consecutive Academy Awards — for 1937’s Captains Courageous and 1938’s Boys Town — while 1942’s Casablanca propelled Bogie to the top of Hollywood’s A-list. “It was a pretty exclusive club,” notes Curtis.

Bogie arrived on the set of The African Queen in 1951 for a scheduled eight-week shoot in the Democratic Republic of the Congo (then the Belgian Congo) with his wife, Lauren Bacall. “[She] was there but strictly as a wife — she used to come out and help with the lunch,” recalls script supervisor Angela Allen, who notes that everyone, including the film’s stars, Bogie and Katharine Hepburn, camped together in “primitive” conditions. The jungles were teeming with hungry ants and leeches. Contaminated drinking water made everyone sick (except Bogie and director John Huston who stuck to alcohol). “Whenever a fly bit me or Huston, it dropped dead,” quipped Bogie.

In the midst of the chaos, Katharine and Lauren became fast friends. “She was loyal, demanding, pure and purely demanding, open, reserved, formally informal, proud, intimidating, exasperating, funny, touching,” wrote Lauren of her friend.

After returning to California, Spencer and Katharine became frequent guests at the Bogart home, where Spencer, who was still married to wife Louise, didn’t have to pretend that Katharine was just a pal. Lauren remembered Katharine as being “blindingly” in love with Spencer.

Spencer and Katharine extended a similar devotion to the Bogarts. When Bogie was dying of cancer, they were near nightly visitors and among the few Lauren would permit to see her dying husband. “Both Bogart and Bacall, I’m sure, were very grateful to them for being there,” says Curtis, who notes that although Lauren asked Spencer to deliver a eulogy, he was too broken up over Bogie’s passing to do so. Hollywood had brought Bogie and Spencer together, but real life had made them friends.