S2·E13 Enemy from Space

In England, a group of space scientists led by Bernard Quatermass, who have developed plans for the first Moon colony, learn that a secret, ostensibly government-run, complex of identical design has been built in a remote part of England and is the focus of periodic falls of small, hollow "meteorites" originating in outer space. Quatermass determines to investigate and uncovers a terrifying extraterrestrial life form which has already begun action to take over the Earth.