Apparently assuming that summertime audiences are not anxious to strain their overheated energies in witnessing heavy, provocative drama, the local summer theatre group has been serving up a light diet of mysteries and comedies, spiced by the presence of some well-known personalities in its recent bill-of-fare. Its latest offering, fully in keeping with that policy, is Patrick Hamilton's "Angel Street," the semi-psychological thriller which enjoyed a successful tour some four years ago and subsequently emerged as a Hollywood epic ("Gaslight") in 1944. If Francis Lederer's performance in the "name" role falls short of the standard set by Vincent Price in the original production, there is a compensating performance by a lesser-known member of the cast to preserve something of the essence of Hamilton's work.

"Angel Street" is the tale of a Macchiavellian murderer who is cheated out of the fruits of his crime, the theft of valuable rubies, and waits fifteen years before returning to the scene, having acquired a moustache and a new, naive, wealthy British wife in the interim, to continue his search for the gems. Since the entire scheme, and a broad hint as to the outcome, are brought out in the first act, it takes worthy performances by the murderer and his unsuspecting wife, who is being methodically driven out of her mind by her spouse, to sustain the terror and suspense in Hamilton's lines.

Francis Lederer, in the role of the scheming Mr. Mannigham, and Helen Shields, who plays his wife, never seem able enough to reach the necessary pitch of excitement. Lederer's villainy is often unconvincingly sinister, while Miss Shields, in the difficult role of a sweet young thing who is preyed upon and is nearly driven to distraction, rarely reaches the emotional heights of fear which could lend a heightened note of terror to the play.

What is lacking in the performances of Lederer and Miss Shields, however, is counteracted in part by Bramwell Fletcher, who plays convincingly the earthy, bustling, hard-working detective who unearths the scheme and unmasks the wrongdoer.

Hamilton's mystery, despite its premature denouement, is properly grim and gripping, and if the actors occasionally fail to inject into the lines all their inherent terror and sombreness of mood, a competent framework is still present. Making all the necessary preliminary reservations about summer productions, they have an interesting chiller on Brattle Street this week.