'The Sentry' by L. Ford Neale , John Huff

At an underground archive installation called the Merrymount Institute, Doctor James Verhyden investigates a recently-discovered cave and finds a clutch of strange eggs hidden in a space in the rock. He and his colleague, Howard Kimper, take the eggs for examination, but after Verhyden has left, Kimper is attacked and dismembered by a huge lizard. Later, electrician Larry Coogan is also killed by the creature. During a press call, the beautiful new police officer Lieutenant Irene Lamont uses her charms to avoid the questions of the reporters, but Kolchak refuses to be sidetracked, and tricks her into revealing the facts about the deaths. Dressed as a surgeon, Kolchak sneaks into the morgue and sees the gruesomely-mutilated bodies of the victims. Then, posing as a potential customer, Kolchak visits the Merrymount Archives and meets sales manager Jack Flaherty; they take the lift down to the installation, which lies two miles below the surface, and encounter a group of complaining mineworkers and an angry Verhyden, worried that his work will be taken away from him. While Kolchak learns that part of the archive is used by the Federal government, is unaware that Lamont has seen his car and is now in pursuit of the troublesome reporter. When the police arrive Kolchak flees into the tunnels; he soon comes across the giant lizard, and only just escapes in a high speed cart; however, he is then caught by the police and arrested. Kolchak’s story is ignored by the authorities, but they nevertheless destroy his pictures of the monster. After he is bailed out by an unhappy Vincenzo, Kolchak elicits the help of ex-convict Arnie Wisemore: he hides inside a crate and manages to infiltrate the archive. Investigating Verhyden’s laboratory, Kolchak discovers the eggs; Verhyden finds him, but just as the scientist is about to kick him out, the lizard smashes through the wall. Verhyden is knocked out, and Kolchak runs off; army officers appear, dressed as water department personnel, and open fire on the creature using machine guns. But the monster shrugs off their attack and easily deals with the soldiers - leaving Kolchak to face the rampaging monster alone...

Darren McGavin (Carl Kolchak), Simon Oakland (Tony Vincenzo), Jack Grinnage (Ron Updyke), Ruth Mc Devitt (Emily Cowles), Kathie Brown* (Lt. Irene Lamont), Albert Paulsen (Doctor James Verhyden), Tom Bosley (Jack Flaherty), John Hoyt (Lamar Beckwith), Frank Campanella (Ted Chapman), Frank Marth (Colonel Brody), Margaret Avery (Ruth Van Galen), Cliff Norton (Arnie Wisemore), Lew Brown (First Detective), Keith Walker (First Reporter), Bill Diez (Second Reporter), Greg Finley (Doctor Phillips), Tom Moses (Doctor Gordon)
*Mrs. Darren McGavin
Directed by Seymour Robbie

TX (US): 28th March, 1975

Notes:
*Featuring Carl Kolchak and Tony Vincenzo