For decades, corporate America has been hoping that Fidel Castro's departure would bring an end to the trade embargo, opening the country to U.S. investment. Almost six months after the Cuban leader stepped aside, temporarily handing over the reins to his brother, there are no signs of a transition to democracy or a market economy. But a tiny closed-end mutual fund run out of Miami is already cashing in. The $14 million Herzfeld ( CUBA) Caribbean Basin Fund (CUBA) invests at least 80% of its assets in companies that derive substantial revenue from operations in the Caribbean region. "We are invested in companies that are doing well now, that will continue to do well, and will get significant new business if the embargo is lifted," says Thomas J. Herzfeld, president and chairman of the fund's eponymous adviser. The Caribbean Basin Fund's share price has more than doubled since Castro fell ill this summer. Over the 12 months ended Jan. 18, it has returned 135%, making it the highest-returning closed-end fund over the past year, according to the Closed End Fund Association. The fund is not exactly a pure play on Cuba, since the embargo prevents any U.S. company from investing directly in the island nation. But Herzfeld says each of the companies it's invested in has the potential to significantly increase its business if the embargo is lifted. For example, Florida East Coast Industries ( FLA), the fund's largest holding at 18.73% of assets, operates 351 miles of freight railroad between Jacksonville and Miami. Herzfeld believes that a large portion of the U.S. freight that would make its way to Cuba if the embargo is lifted would have to use those rails.