A sniffer dog called Buzz helped detectives make Shetland's biggest seizure of drugs.
The High Court in Edinburgh heard the drugs had a high value
Officers also foiled the first attempt to bring a dealer-sized supply of cocaine to the island when they stopped Stuart Riach leaving a ferry.
Courier Riach, 51, of Glasgow, admitted being concerned in the supply of heroin, cocaine and amphetamine worth about £45,000.
Sentence was deferred on Tuesday at the High Court in Edinburgh for reports.
Riach, of Sunnyside Drive, Blairardie, admitted being concerned in the supply of the drugs on 14 September last year.
Police had been tipped off to look out for a foot passenger arriving on the ferry from Aberdeen.
Officers kept watch at the Holmsgarth terminal and saw Riach with two holdalls.
Plain clothed police stopped him and a later search in Lerwick police station found a white sports sock containing cocaine in one of the holdalls.
There was also a box, sealed with tape, which contained two bags of heroin.
Riach was then taken to an address in Park Wynd, Sandwick, and on the way admitted that there was "speed" in the house.
The court heard that black labrador Buzz was brought in to search the premises and found a carrier bag and soup carton in the freezer, both containing amphetamine.
Riach insisted that he only intended to sell the amphetamine and that as far as the heroin and cocaine were concerned he was just a courier.
Police experts said the 752g of amphetamine, if cut or diluted, could fetch £23,960, the 247g of heroin could reach £19,760 on the streets, and the 22g of cocaine was priced at £1,320.
Advocate depute John Halley, prosecuting, said: "This is the largest seizure of controlled drugs made in Shetland and the first time cocaine, in anything other than small, personal quantities, had been seized in the island."
Judge Lord McEwan called for background reports and allowed Riach to remain on bail pending sentence next month.