admiralty officers and imprisoned first at Fleet prison and then at Marshalsea. He might have remained there for some time if not for the intervention of the lord admiral, Edward Fiennes de Clinton and the secretary of state, William Cecil. With their help, Frobisher was free again in March 1570. The terms of his release are unknown but it appears that Frobisher was required to undertake certain assignments at the direction of the Privy Council. In October 1571 he was commissioned to command four ships in the search for pirates and smugglers along the English coast. There is no indication that he had any success in this effort. In 1572 he was directed to the Irish coast to provide logistical support for the English campaign against the Desmond Rebellions. Starting in 1571 Frobisher was involved in various plots that ran counter to government interest. He possibly had the tacit approval of the Privy Council, suggesting that he may have been working as a double agent. He was briefly associated with a plan to help the Earl of Desmond flee England; then a proposal to lead a group of disaffected English mercenaries to seize Flushing for the Spanish king; and finally, in 1573 a plot to capture the English rebel, Thomas Stukley. According to the Dictionary of National Biography, the first direct notice of Frobisher apparently is an account in the State papers of two interrogations in 1566, "on suspicion of his having fitted out a vessel as a pirate". On 21 August 1571 Captain E. Horsey wrote to Lord Burghley from Portsmouth that he "has expedited the fitting out of a hulk for M. Frobisher"; this is the earliest mention of Frobisher being in the Crown's employ. Burghley, then chief minister of the Queen, became Lord High Treasurer in 1572. From the latter part of 1571 to 1572 Frobisher was in the public service at sea off the coast of Ireland. North-west passage Throughout much of the sixteenth century, the feasibility of a northern route to Cathay and the East Indies was debated and tested by England. In 1508 Sebastian Cabot led one of the first expeditions to search for a north-west passage. In the 1530s, Robert Thorne and Roger Barlow tried unsuccessfully to interest Henry VIII in a plan to sail directly over the North Pole to China. In 1551 a company of English merchants (later known as the