The young Alexios was imprisoned in 1195 when Alexios III overthrew Isaac II in a coup. In 1201, two Pisan merchants were employed to smuggle Alexios out of Constantinople to the Holy Roman Empire, where he took refuge with his brother-in-law Philip of Swabia, King of Germany.

According to the contemporary account of Robert of Clari, it was while Alexios was at Swabia's court that he met with Marquis Boniface of Montferrat, Philip's cousin, who had been chosen to lead the Fourth Crusade, but had temporarily left the Crusade during the siege of Zara in 1202 to visit Philip. Boniface and Alexios allegedly discussed diverting the Crusade to Constantinople so that Alexios could be restored to his father's throne. Montferrat returned to the Crusade while it wintered at Zara and he was shortly followed by Prince Alexios's envoys who offered to the Crusaders 10,000 Byzantine soldiers to help fight in the Crusade, maintain 500 knights in the Holy Land, the service of the Byzantine navy (20 ships) in transporting the Crusader army to Egypt, as well as money to pay off the Crusaders' debt to the Republic of Venice with 200,000 silver marks. Additionally, he promised to bring the Greek Orthodox Church under the authority of the pope.