Even if you don't know Kiritsugu has an underling, you do know he's got a servant.
You really should be able to understand that Kiritsugu could have asked Saber to kill Archibald and Sola before he is bound by the contract...
Wouldn't ordering Saber to kill them be the same as breaking the contract since he can't intend to harm them thus once the contract is in place he can't order anyone to harm them.
You are here alone again
In your sweet insanity
All too calm, you hide yourself from reality
Do you call it solitude? Do you call it liberty?
When all the world turns away to leave you lonely