Hossain began his practice at Original (one of the oldest law firms on the Indian subcontinent, which had established a division in East Bengal during the 1950s), and was invited to join the firm by lawyer Abul Ahmad. At Original, Hossain worked with two Englishmen and Justice Mohammad Hossain. Hossain was at Original from 1959 to 1962, when he came into frequent contact with barrister and former prime minister Huseyn Shaheed Suhrawardy. Pakistan had come under military rule after a 1958 coup, and Hossain has recounted that he and Suhrawardy often zigzagged their car through Dhaka's streets to confuse (and evade) Pakistani-intelligence vehicles. Through Suhrawardy, Hossain came into contact with Sheikh Mujibur Rahman. He has said that Rahman predicted the collapse of Ayub Khan's regime in 10 years (which it did, in 1969).