The following edition of the text was used in the creation of this study guide: Kirkwood, Lucy. Mosquitoes. Nick Hern Books, 2017. Kindle AZW file.

The play is set in England and Geneva, Switzerland, between 2006 and 2008. In Act 1, in 2006, sisters Alice and Jenny discuss Jenny’s fear of ultrasounds, which she believes might harm her unborn baby. Alice reassures her, but Jenny insists on controlling her own decisions. A personified Boson particle, unseen by other characters, enacts the Big Bang with an exploding apple. Alice’s teenage son, Luke, appears, and The Boson notes he has a new friend request. In Geneva, Luke chats online with Natalie, a girl from school, revealing his suspension for hacking the school’s parent portal and mentioning his mother’s work searching for the Higgs Boson at CERN. When Natalie teases about his mom creating a black hole, Luke offers to hack her dad’s work system, and she stops replying. Later, at their apartment, Luke complains about his school and Alice’s recent trip away to support Jenny. They discuss his father, who left after doubting the work being done at CERN, fearing it might reveal the universe’s instability. Alice dismisses these fears and reassures Luke he’s different from his dad.

In Act 2, in 2008, a year later, Jenny visits Alice and Luke in Geneva. Jenny recounts accusing two men of being terrorists on her flight, and it becomes apparent her baby, Amy, has died. At CERN, Alice prepares for the Large Hadron Collider’s launch, facing media questions about its safety. After an initial failure, the collider successfully launches. Later, Luke explains to Jenny that he was beaten up at school after putting an HPV leaflet in a girl’s locker; Jenny dismisses his actions as immature and criticizes him harshly. She guesses Alice’s phone passcode and arranges a meeting with Henri, Alice’s boyfriend, under false pretenses. At the meeting, she offends Henri, blames vaccines for autism, and attempts to seduce him. Henri rebuffs her, blames her for Amy’s death, and leaves. Jenny begins an overdose, but Henri returns and saves her. Back at Alice’s apartment, Luke is missing. Henri reveals Jenny’s erratic behavior and suicide attempt, leading to a heated argument where Alice defends her sister. Jenny apologizes for her actions, and their mother, Karen, enters in a confused and volatile state. Karen blames Jenny for Amy’s death and spanks her in a fit of rage. After Karen leaves, Jenny and Alice reconcile, hugging as Jenny breaks down. Jenny vomits as a result of being given charcoal at the hospital to counteract her overdose.

Act 3 opens with The Boson addressing the audience while cleaning up Jenny’s vomit, speaking condescendingly and erratically about the end of the world. In Geneva, Natalie finds Luke in a park and urges him to come home, but he refuses. At Alice’s apartment, she and Jenny pray together, revealing painful memories—Luke’s father’s disappearance and Jenny’s guilt over Amy’s death. At Natalie’s house, she tricks Luke into sharing an explicit photo, then distributes it, leaving him distraught. Back at Alice’s, Karen explains her reluctance to see a doctor about dementia due to assisted-suicide restrictions. Luke returns, upset about his life in Geneva, and Alice refuses his request to move in with Jenny. Jenny suggests everyone living together in England, but Alice insists she must stay in Geneva for her work. Later, Karen reflects on love’s fragility and her struggles with postnatal psychosis. She falls asleep on Jenny’s lap after insulting Jenny, unaware that Jenny is there. Jenny silently cries and receives a phone call.

In Act 4, Jenny meets Luke outside CERN, where he confesses to planting a virus in the system using Alice’s laptop and begs her to take him back to England without telling Alice. After Luke smashes the laptop in frustration, Jenny tells Luke to leave and reassures him that she has a plan. After Luke leaves, Jenny is confronted by a security guard. Later, at the police station, Alice and Jenny argue bitterly. Jenny has lied to everyone and claimed that it was her who planted a virus in the system at CERN. There has been significant damage done to the machinery but Alice believes it must have been caused by something else because she doesn’t think Jenny is intelligent enough to have caused this much damage. Alice blames Jenny for Jenny’s daughter Amy’s death and suggests that she was never cut out to be a mother. Back at Alice’s apartment, she listens to Luke’s music made from the sound of the Higgs Boson particle sounds and, captivated, sees The Boson in him. The Boson delivers a monologue, recounting how a scientist makes a discovery that, centuries later, plays a pivotal role in creating a new universe—a "lifeboat" (131) for humanity. Despite their differences, the scientists who build this universe are united in hope, stepping into the new creation with the thought, "this time / we’re going to get it right" (133). In the final scene Alice visits Jenny in England, their relationship strained since Jenny confessed to infecting Alice’s workplace with a virus. Alice updates Jenny on her life, sharing that Luke is happier at a new school. Jenny surprises Alice by revealing she is pregnant. Alice, initially skeptical due to Jenny’s drinking, smoking, and overdose during early pregnancy, learns that the baby is healthy. Jenny affirms her decision to keep the child, placing Alice’s hand on her stomach.