Venom

Müller and Louise outline a plan to abduct Philip Hopkins, the grandson of Howard Anderson. Louise goes undercover as a maid in Philip's mother's household and uses the position to gather information and enable the kidnapping. She also persuades Dave Averconnelly, the family chauffeur, to join the plan.

On the day of the kidnapping, Müller tricks Howard and Ruth into leaving the house under pretexts. Louise and Dave seize Philip and kidnap him from the residence. The family returns to find the boy missing, triggering the crisis.

Philip goes to retrieve a pet snake, creating an opportunity for a lethal swap. The black mamba intended for Dr. Marion Stowe is swapped with Philip's harmless pet snake. The dangerous snake is now inside the Hopkins home, a latent threat to everyone present.

The black mamba is released and attacks Louise, biting her on the face repeatedly before fleeing into the ventilation system. Louise dies soon after from the venom. The murder intensifies the tension inside the house as the criminals improvise with the hostages.

Müller and Dave take Howard and Philip hostage, cementing the standoff in the residence. Louise's death accelerates the danger to the hostages and concentrates the criminals' efforts. Dr. Stowe and the police become aware of the crisis and its deadly wrinkle.

Dr. Marion Stowe contacts the police after discovering the mix-up and the growing danger. She explains the black mamba complication and provides critical information for responding officers. The situation shifts toward a coordinated law-enforcement response.

An initial police officer arrives at the Hopkins residence to negotiate and assess the situation. Dave shoots the officer with one of Howard's rifles, killing him but enabling a call for backup. The incident triggers a larger police response.

Commander William Bulloch arrives with a plan to seal off the street and negotiate for the safe release of the hostages. He refuses to yield to Müller's demand for transportation and a large sum of money in various currencies. Negotiations begin as the risk of violence grows.

Bulloch and Dr. Stowe warn both the kidnappers and hostages about the black mamba's presence. Dr. Stowe brings an anti-venom case and prepares to assist if needed. They coordinate to keep the situation controlled while authorities seek a breakthrough.

Bulloch discovers a secret entrance through the cellar and orders his team to prepare an entry. He and two officers move to investigate the hidden route while the standoff continues inside. The discovery raises the possibility of a tactical breach to end the crisis.

Dr. Stowe suggests turning off the central heating to drive the black mamba into a coma. The cooling plan aims to reduce the snake's activity and make conditions safer for the authorities. Building controls are adjusted in hopes of a quicker resolution.

Dave and Howard climb into the cellar at the same time as Bulloch's team attempts entry. The black mamba launches an assault, forcing Bulloch and the officers to retreat. Dave is unable to escape and is killed by the venomous snake.

Müller offers Bulloch a severed finger, falsely claiming it belongs to Dr. Stowe, to pressure him into compliance. Bulloch agrees to bring Müller's getaway car to the door under the ruse. The deception gives Müller's crew a tactical edge while the situation remains unstable.

Müller forces Dr. Stowe onto a balcony and tries to extract information about the hostages' status. Philip and Howard notice the approaching danger and trigger a risky move with the mamba. Snipers open fire, killing Müller and the snake as they tumble from the balcony.

The hostages are rescued and Ruth embraces Philip as the danger ends. The final shot reveals the black mamba had laid an egg in the vents, which hatches and slithers away, suggesting a lingering threat beyond the immediate crisis. The scene closes on a note of unresolved danger.