Arsenal's £60m move for Borussia Dortmund forward Pierre-Emerick Aubameyang hinges on two more transfers being agreed.
And Gunners striker Olivier Giroud may have the biggest say in whether the deal is completed before Wednesday's 23:00 GMT deadline.
Arsenal have agreed a fee with Dortmund and personal terms with Gabon international Aubameyang, 28, but the German club will only sanction the move if they get a replacement.
BBC Sport's David Ornstein guides us through the complicated Aubameyang transfer merry-go-round...
Option one - the straight swap
Giroud was lined up as part of the deal to replace Aubameyang at Dortmund.
Arsenal boss Arsene Wenger is fond of Giroud, but the 31-year-old France striker has been told he will not get the game time he needs before this summer's World Cup in Russia.
But Chelsea, in the market for a tall target man, make an offer to Giroud, who would prefer to stay in London. So...
Option two - the three-way deal
Dortmund turn their attention to Blues striker Michy Batshuayi, who is allowed to leave - on loan - in January. The 24-year-old Belgium international is keen.
A seemingly simple solution presents itself: Aubameyang to Arsenal, Giroud to Chelsea and Batshuayi to Dortmund.
However, Chelsea are not keen to pay Arsenal's asking price for Giroud - a reported £30m-£35m. So...
Option three - enter Llorente
Exploring other options, Chelsea then hold talks with Tottenham to swap Batshuayi for Spanish forward Fernando Llorente, 32.
The Blues prefer a loan, Spurs are keen on a permanent deal - but Batshuayi rejects the move anyway because he wants to be a first-choice striker, not go from being behind Alvaro Morata at Stamford Bridge to being back-up for Harry Kane at Tottenham. So...
Option four... back to option two
Let's back this up and return to Aubameyang going to Arsenal, Batshuayi joining Dortmund and Giroud moving to Chelsea to complete the equation.
But will Arsenal reach an agreement with the Blues?
If not, will Chelsea find an alternative to replace Batshuayi?
If not, and Batshuayi stays, will Dortmund find another striker to replace Aubameyang? The Bundesliga side have previously said he will not be allowed to leave without an alternative in place.