Essam Tasir was a former college roommate of Sayid at the University of Cairo, where he earned a degree in philosophy. Essam's wife, Zahra, was killed in the bombings of civilian areas in Baghdad (during the American invasion of Iraq), while shopping for a dress. In the events of his wife's death, the then angry and desperate Essam is lured into a terrorist cell in Sydney, Australia, that aims to disrupt the US-lead Coalition prison on Iraq. Initially bribed with the knowledge of Nadia's whereabouts, Sayid was recruited by Agents Alyssa Cole of the CIA and Robbie Hewitt of the ASIS at the Heathrow Airport, in order to hook up with Essam and recover 300 pounds of stolen C-4 explosive stolen by his cell.

Sayid talking to Essam. ("The Greater Good")

To gain the trust of the cell, including Haddad, Sayid's first move was to uncover a bug planted in their apartment, while pretending to talk to Essam about their good time in Sharm el-Sheikh. Later, Essam confides in Sayid that he was chosen to be the martyr in a bombing operation using the C-4 explosive. However, Essam revealed his strong doubts about his role and the legitimacy of the whole operation. As he explained to Sayid, his main concerns were not fear of his own life, but the conflict he struggled between the just and peaceful teachings of Islam and the opposing role he will take in the killing of innocent lives during the operation.

Consequently, Sayid asked Agents Cole and Hewitt to let him save Essam and bring him in. However, they harshly refused and ordered Sayid to convince Essam of shedding his doubts and going on with his role, only to enable the uncovering of the explosive's location. When Sayid refuses to cooperate, he is blackmailed with threats of arresting Nadia in false charge at his failure to talk "Essam into blowing himself up".

Essam and Sayid's last conversation. ("The Greater Good")

On his return, the blackmailed Sayid used the memory of Essam's dead wife to remind him of the injustice that fell upon him, and thus fuel his will to avenge her, discarding any other concerns he had for the "greater good". As Essam listened, he gradually agreed to accept his mission, and asked Sayid to come along with him for support.

Unable to stand his guilt, Sayid confessed his true role and cause to Essam before they set on their mission, and asked him to take this last chance in escaping. However, Essam was by that time unstable and distraught. As he condemned Sayid's trickery over a woman, he initially threatened to kill him and then immediately shot himself instead. On the knowledge that Essam's body will be unclaimed, Sayid insisted on claiming it and remained in Sydney to give Essam a proper Muslim burial. Thus, he was delayed to be on Oceanic Flight 815.