He figures he’ll surprise her; he finally feels comfortable in this newer, older body (though he’s still unsure on the kidney color), and he wants to see his wife- preferably sometime later in their timeline. The TARDIS seems to have other ideas though; she takes him to the library of Luna University, practically throws him out the doors, and promptly locks him out.
"I get it, I get it, go talk to the wife!" he mutters under his breath, in the Scottish brogue that still catches him off-guard. He heads right for the top floor, where he knows River prefers to study; it’s quieter and more blocked off, allowing her to have her own space without anyone interrupting.
He finds her in the back corner, hair a messy array around her shoulders and pen cap in her mouth. She’s bent over a book that looks as ancient as him, dust particles in the air; she sneezes as he comes closer, and with a soft smile he says, “Bless you.”
She looks up, startled- she’d evidently not heard his footsteps, engrossed in her book as she was. She gives him a tentative smile, pushing some of her never-ending hair back behind her ear. “Thank you. Are you a professor here? Students rarely come to this section of the library.”
It takes him only a moment to realize; she doesn’t recognize him. She doesn’t know him, doesn’t know this face; this is a River who is young and free and still in the process of discovering who she is. He swallows, offering her a half-smile he’s sure looks pained.
"Not quite, dear," he replies, reaching into the inside pocket of his suit and pulling out a length of satiny cloth; River’s lips part as he lets the bowtie pool on the desk between them.
"Doctor?" she whispers, rising from her seat and reaching a hand out, fingertips whispering across the back of his hand. "But you’re-"
"Old?" he supplied, amusement coloring his tone as River flushed, biting her lip.
"I was going to say mature," she replied, rounding the desk and lifting her hand, cupping his cheek gently as the other made its way to the center of his chest, resting directly between his hearts. "I rather like the gray. It suits you."
"You suit me," he murmurs, nose buried in her hair and arms around her waist. "What do you say we leave these dusty books behind and go on an adventure, River Song?"
"Only if you promise to have me back by dinner; I have a test tomorrow," River says, pulling back slightly to look at him sternly, though there was teasing in her eyes. The Doctor leaned forward, pressing a kiss to the tip of her nose gently, delighting in the way she crinkled it afterwards.
"Anything you say, m’dear."