Does the line "You wanted to see me, Inspector?" occur in "The Hollow" more times than is usual for an Agatha Christie play?

Perhaps it's just that after so many seasons of so many Agatha Christies, this line, with such variations as the ominous "I believe the Inspector wants a word with you," is now a permanent part of the air around Olney. "The Hollow," a 1951 mystery thriller set at a house party of English country cousins, opened the Olney Theater's 30th season this week.

There is an awfully good version of the eccentric matron who takes a cheerful interest in having a murder occur on her drawing- room rug; this one is played by Paddy Croft, and says things like, "Now, where did I lay my eggs?" And there is an expert rendition by Pat Karpen of the nervous character whose jumpiness is partly comic and partly scary.

Otherwise it's rather an average show -- with the qualification that averages are high at Olney, and certainly Agatha Christie's averages are impressive ("The Hollow" was followed by "The Mousetrap," whose London production also is in its 30th season). "The Hollow" is the name of the house where the murder takes place, and can also serve as a description of the state of the heart of the victim. There are not dozens of victims, probably as much of a disappointment to that genteel lady of the house as to thriller fans, and the motives -- real, as well as red-herring -- are banal. The play lasts two and three-quarters hours, and much of that time taken is up by the characters explaining the mechanics of the situation to one another.

Under Leo Brady's direction, it moves along nevertheless. But there are few of the quirky touches that are needed to sustain such set characters -- snooty butler, vainglorious movie star, callous roue, hopeless lovers -- going through such routine paces.

THE HOLLOW -- At the Olney through June 27.