The story

One night in bed, the promiscuous Connacht Queen, Maeve, quarrels with her
husband Ailill. They argue over who has the most wealth. Ailill doesn't
like the suggestion that he's a kept man. "Her words were sharp they cut
him deep, in a war between the sheets". Ailill's magnificent White Bull is
the deciding factor in their subsequent measuring of possessions. Maeve's
a bad loser. Mac Roth, her messenger, goes to Cooley to rent the famed
Brown Bull for a year, thus giving Maeve the decider. "I once told her where
she could find her dream". The Bull's owner is agreeable until Mac Roth and
his party get very drunk and reveal that had they not been allowed to borrow
the bull they would have taken it by force. The deal breaks down. They go
home emptyhanded. Maeve decides on war.
Having marshalled all her warriors, and allies from Munster and Tara, and
with Ailill's six brothers and their armies standing by Maeve receives
favourable omens from her Druids. The long march to Cooley begins. "The
champions and the Seven Sons are come to take away the Donn". However, a
sorceress appears and warns Maeve of impending defeat at the hand of Dearg
Doom, Cu Chulainn. "Saw the host stained red in war, saw the hero-light
around the head of a dragon-boy". The warning is ignored.
Meanwhile, the men of Ulster are ill with labour pains - the legacy of a
curse put on them for their inhuman treatment of a pregnant woman. The one
man exempt from this curse is Cu Chulainn, whose very birth is shrouded in
mystery. Singlehandedly he takes on the defence of Ulster, harassing Maeve's
soldiers, "And like a hawk I'll swoop and swoop again", beheading those who
stray from the main force. "You can hear me shout 'two heads are better than
none. One hundred heads are so much better than one'". Cu Chulainn is a
hard man. Originally called Setanta, he became known as Cu Chulainn, the
Hound of Culann, because of his savagery. As the Connacht losses grow
greater, the deposed King of Ulster, Fergus MacRoich, who is having a secret
affair with Maeve, meets Cu Chulainn and arranges a treaty. Cu Chulainn
agrees to singlehanded combat with any Connacht champion provided Maeve's
army does not advance. One by one, day after day he defeats each warrior
until eventually he faces his old foster-brother and close friend Ferdia.
Cu Chulainn pleads with Ferdia to leave. "But Ferdia just laughed and shook
his golden head and then they fell to battle again". For three days they
fight at a ford and appear evenly matched until on the third day Cu Chulainn
flies into a rage and lets loose his supernatural javelin, the terrible Gae
Bolga, which destroys his friend. As Ferdia falls Cu Chulainn catches him
and carries him to the riverbank, lamenting. "Life was a game, Now I miss
your name your golden hair". Then overcome by despair Cu Chulainn abandons
the fight.
Maeve's army moves south with the stolen bull. The Ulster men rally and
with Cu Chulainn in their ranks they give chase. "But before you hit off,
let me say this time you bit off more than you can chew". The Morrigan,
Queen of Demons, who has been encouraging slaughter all along, prophesies
the outcome. In the battle which follows the Connacht army is routed.
"It seems our fortunes lied despite our gain. Our tears fall like our
pride". Maeve's life is spared by Cu Chulainn. As the Ulstermen are taking
the Brown Bull home, they meet Ailill's Bull, the White-Horned one. The Donn
immediately attacks the White. "You can fool them alright but can you fool
the beast"? All day and night they are locked in combat. Morning sees the
Donn victorious. The armies consider destroying him, the cause of all their
suffering, but leave him as, dying, he staggers homewards.