Ó hUid was arrested in 1940 and interned in Crumlin Road Jail, he would later be transferred to Derry Prison two years later before being sent back to Crumlin Road following another two years. Ó hUid was released on 8 December 1945, one of the last internees to be freed. In prison he acted as head of the internees and organised classes, performed plays and produced the magazine Faoi Ghlas for inmates, striving to teach the Irish language to the prisoners. By 1943, Ó hUid had grown disillusioned with the IRA following the Stephen Hayes fiasco and intended to resign, but refused to declare to the authorities that he would no longer be associated with Irish republicans. In December 1944, Ó hUid joined Glún na Buaidhe in prison. He wrote the novel An Bealach chun an Bhearnais, which would be published in 1949.
