Yusuf was a chemist who specialised in powerful sedatives to keep people dreaming for long periods of time. He held a shop in Mombasa where people would come to dream for long periods of time.
Dom Cobb came to Yusuf with Eames and Saito, wanting a sedative powerful enough to support three levels of dreams. Yusuf agreed to come on the job with them, which was the inception job on Robert Fischer. He boarded a 747 with the rest of the team, and put everyone under including himself.
On the first level of the dream, the team kidnapped Fischer but were attacked by his militarised projections. They escaped to a warehouse, where Yusuf revealed that if anyone died in the dream the sedative would send them to Limbo. They then all went into a van and put themselves under for the next level of the dream. Yusuf stayed awake, driving the van to avoid the projections who were chasing them.
Yusuf escaped from the projections, flipping the van over at one point. He then reached a bridge and at the required time, drove the van off the bridge. The bridge hit the water, kicking all of the dreamers out of their sleep. They swam to shore, where Fischer announced that he would be breaking up his father's empire, indicating that their job had been successful. Yusuf woke up on the plane, and entered America.