London. British spy, Ian Munro, is

London. British spy, Ian Munro, is briefed by his
boss Naylor about the suspicious deaths of people
and animals in Lahti, Finland – the possible result of
a toxic gas. Munro travels to Finland to investigate.
There, a local contact, Pentti Virolainen, is shot dead
while Munro looks on, unable to intervene. Munro
calls London for further orders. Meanwhile, he
reads an article about Finnish businessman Jorma
Lappalainen, owner of a bioengineering business.
That evening, Munro meets the lovely Riitta Koivisto,
who seems rather too curious about him. At midnight,
Koivisto visits him in his hotel room, and they spend
the night together. However, when Munro wakes up,
he realises he has been drugged and discovers his room
has been searched.
The next day, Munro is given an address to visit. Before
doing so, he realises he is being followed. Munro plays
for time, and calls London for help. Still trying to
evade his pursuers, Munro returns to the hotel, where
he escapes detection by pretending to be the drinking
partner of a hotel guest sleeping off a binge. Munro
remains in the safety of the guest’s room until he
receives a message from London, which is a car number.
Disguised in the hotel guest’s clothes, Munro first deals
with the henchman guarding the rear of the hotel.
Leaving him unconscious, he rushes to the front where
he alerts the other henchmen to a fight in progress at
the rear. Munro escapes in the car parked outside.
In the suburbs of Lahti, he meets Sirpa Virolainen,
sister of the murdered Pentti Virolainen. She tells
Munro that Pentti worked for a bioengineering
company called Bioratkaisut, the same company that
Koivisto worked for. Pentti discovered the company
was developing poison gas, and spoke about this to
a British scientist, an action which cost him his life.
Sirpa gives Munro a piece of paper left by Pentti,
probably a chemical formula.
Munro realises he must take Sirpa to a place of
safety, and drives her to Helsinki. On the way he
sees two jeeps following. He manages to shake off
one jeep, but the other forces Munro’s car off the
road. When Munro and Sirpa regain consciousness,
they are held captive by Jorma Lappalainen, who
admits that his companies are developing poison
gas for a foreign power. Lappalainen locks them in
a sauna, and turns up the temperature to a lethal
level. Munro and Sirpa manage to escape, but
are intercepted by Lappalainen. Sirpa is shot but
Munro eventually disarms Lappalainen. Rather
than face justice, Lappalainen commits suicide by
drinking poison.
Fortunately, Sirpa has only been slightly wounded.
After giving evidence to the authorities and learning
that Koivisto is Lappalainen’s sister, Munro takes
Sirpa home. The next day, when about to leave for
London, Munro receives a call from Koivisto, who is
holding Sirpa hostage at the top of a ski jump.
Munro arrives to find Sirpa apparently dead, and
Koivisto threatening him with a gun. He realises his
only chance is to keep her talking. A groan from Sirpa
distracts Koivisto and Munro seizes his chance to
disarm her. A fight ensues, ending with a lethal blow
to Koivisto’s neck. Munro is able to save Sirpa’s life.
The case is over